RIGA, Latvia—Tikhon Dzyadko greeted the audience of TV Rain, once Russia’s main independent television channel, with a trademark phrase, just like he had countless times before.

“In Moscow, it is twenty zero-zero,” he said at the start of the channel’s 8 p.m. news program. “Over the next two hours we will tell you the main news of the day.”

But this time, Mr. Dzyadko, TV Rain’s editor-in-chief, wasn’t in Moscow. He was speaking from Riga, Latvia’s capital city, where the channel relaunched operations last week, more than four months after it was forced off the air by Russian authorities.

In the wake of Russia’s invasion of Ukraine, the Kremlin adopted legislation punishing the dissemination of false information about the activities of Russia’s armed forces with up to 15 years in prison. Kremlin spokesman Dmitry Peskov said at the time that the law was needed because of “the absolutely unprecedented information war that was unleashed against our country.”

Russian authorities have since blocked the websites of dozens of the country’s independent news media for not toeing the official line on the war, which Russian President Vladimir Putin describes as a special military operation aimed at ridding Ukraine of fascism. Hundreds of journalists have fled the country, while 12 have been charged with violating the new law and three of them are being held in pretrial detention, according to human rights lawyers.

Now, in capitals across Europe, independent Russian newsrooms have regrouped and are trying to reach audiences in Russia swamped by the state’s messaging about its invasion.

“I consider myself also to be at war,” Mr. Dzyadko said in an interview in Riga last week before launching into a program that covered the latest news from Ukraine and the recent wave of arrests in Russia. “My job is for my work here to lead to the possibility that we can get home as soon as possible.”

Ekaterina Kotrikadze, news director and an anchor at TV Rain, watched as the first broadcast got under way.

TV Rain hopes to reach its Russian audience over YouTube.

The journalists are under no illusions that they have a simple path forward. They acknowledge a raft of challenges, from securing stable financing streams without sacrificing their independence to convincing more Russians to use virtual private networks, or VPNs, to bypass Moscow’s blocks on their websites and those on foreign social-media platforms.

The biggest obstacle might be expanding an audience that was already smaller than that of state media before the war.

Press freedoms have steadily eroded since Mr. Putin came to power in 2000 and began bringing the country’s television stations under state control. Last year, authorities began designating dozens of individual journalists and entire outlets as “foreign agents,” a label with Soviet-era connotations of espionage that crimped their access to revenue from advertisers. Some have been declared undesirable organizations. Journalists working with those risk six years in prison.

At the time, Kremlin spokesman Mr. Peskov defended the moves.

“There are attempts to interfere in our domestic political processes from abroad, and NGOs, journalists and media are often used for this purpose,” he said.

Since the invasion, authorities are doing away with the independent press altogether, blocking the websites of at least 200 independent Russian media outlets, according to Galina Arapova, director of the Mass Media Defence Centre, a Russian nonprofit organization. Dozens more have chosen to stop their operations or self-censor by not covering the war, she said.

The Prosecutor General’s Office, which is responsible for blocking the outlets, didn’t respond to a request for comment.

“Any Russian journalist has three choices,” said Roman Anin, founder and editor-in-chief of iStories, an investigative news website branded an undesirable organization in March. “Stay in Russia and go to prison and don’t do anything further. Stay and shut up and don’t do anything. Or leave and do something. We decided to leave and do something.”

Having relocated to a European city that iStories doesn’t name publicly, and kept up its work on grant money, Mr. Anin said one of the more important projects the outlet is pursuing is identifying Russian soldiers alleged to have committed war crimes in Ukraine. The outlet continues to work with some journalists in Russia without publishing their names for their protection, and doesn’t disclose its location or the source of its funds for security reasons, Mr. Anin said.

Some outlets see their chief mission as not abandoning their audiences.

Kirill Martynov, editor-in-chief of Novaya Gazeta Europe.

“We have a responsibility to people in Russia who haven’t been lost to propaganda. Primarily to show them that they’re not alone,” said Kirill Martynov, editor-in-chief of Novaya Gazeta Europe.

The outlet, a spinoff of Novaya Gazeta, Russia’s top investigative newspaper whose editor Dmitry Muratov was the co-winner of the Nobel Peace Prize last year, launched in Riga in April. It employs more than 50 journalists across various locations, all of whom worked for the paper, which has paused operations in Russia until the war ends after receiving warnings from the state communications regulator. On Tuesday, the regulator asked a Moscow court to revoke Novaya Gazeta’s license anyway, the Basmanny district court said. The hearing will take place on Sept. 15, according to Nadezhda Prusenkova, an editor and spokeswoman for the paper.

The newsrooms have mainly coalesced in Riga partly because of the ex-Soviet country’s prevalence of Russian speakers and its proximity to Russia, but also because the Latvian authorities have welcomed the journalists, despite halting tourist visas for Russians after the invasion.

“Our interest is to get as much information as possible that is objective to influence the Russian public about the ongoing war in Ukraine, about the true intentions of our government, the European Union, NATO,” said Latvian Foreign Minister Edgars Rinkevics. “While you will never expect an immediate change of attitude, you still work in the long term trying to get objective information, independent news to the public that is currently only getting propaganda.”

Latvian Foreign Minister Edgars Rinkevics has welcomed independent Russian media organizations to base themselves in Riga.

Photo: Kristine Madjare for The Wall Street Journal

Mr. Rinkevics compared the current situation to the Cold War, when radio stations like Voice of America, Radio Free Europe/Radio Liberty and the British Broadcasting Corp. beamed their broadcasts into the Soviet Union. While independent and state-backed polling shows that around 80% of Russians support the offensive against Ukraine, political analysts suggest the number is closer to a slim majority and Mr. Rinkevics believes they can be won over in the long run.

Mr. Rinkevics said the Latvian government’s support of the Russian newsrooms consists of visa support and helping with networking, and he and the newsrooms’ editors said they do not and will not receive any government financing.

Novaya Gazeta Europe launched with funding from JX Fund, an initiative led by Reporters Without Borders, and hopes to use the three million unique monthly visits to its website to launch a crowdfunding effort and begin hosting events for its supporters.

Working mainly out of Vilnius, the capital of Lithuania, the Mediazona news website also relies on a mix of grant money and crowdfunding, said its editor-in-chief, Sergey Smirnov. It has continued sending reporters under cover to Russia’s courts to cover cases of Russians tried for criticizing the war, and has kept a tally of Russian soldiers killed in Ukraine from publicly available sources. Its count is more than triple that of the Russian Defense Ministry, which last published a toll in March, totaling 1,351.

Brand new outlets have popped up, too. Verstka, with 10 journalists based between Prague, Tbilisi in Georgia, Vilnius and Russia, launched in late April and is keeping a tally of Russian soldiers who have deserted. Verstka’s website was blocked in Russia within weeks.

“The Kremlin wants society to think that it’s consolidated” broadly behind the war, said Lola Tagaeva, the outlet’s founder, who emigrated to Prague three years ago. “But there are other people who are skeptical, mainly young people, who most often don’t speak up or act. These are the people we need to reach.”

Getting information into Russia is difficult, though, and the journalists say part of their work now consists in educating Russians about VPNs. Daily demand for VPNs in Russia is 2000% higher than prior to the invasion, according to Top10VPN.com from London-based research company PrivacyCo.

While Russia blocked Facebook, Instagram and Twitter early in the war, YouTube remains available and is one of the few platforms from which Russians can get uncensored information. That is where TV Rain says it is planning to reach its audience.

Founded in 2010, TV Rain, which calls itself the “optimistic channel,” quickly grew a substantial audience before Russian networks removed the channel from their cable bundles four years later after it began to run up against the authorities, depriving it of most of its viewers and leaving it dependent on subscribers.

After fundraising for its relaunch, TV Rain is pivoting toward monetizing views on YouTube—where it has 3.3 million subscribers—plus crowdfunding and earning income from cable packages in countries with a prevalence of Russian speakers, said Mr. Dzyadko. The channel is launching studios in Amsterdam, Paris and Tbilisi, but its main task for now is restoring its viewership after its fourth-month pause, he added.

Kulle Pispanen, a former TV Rain employee who helped launch the channel in Moscow, was in its new studio, hosted by TV3 Latvia, a commercial channel, for its return last week. Everything else aside, she said, the most important thing was that independent Russian media still exists.

“No matter how much they are scattered, they grow back, like the spores of a dandelion,” she said.

Write to Evan Gershkovich at evan.gershkovich@wsj.com