A British citizen had his assets frozen by Britain’s Foreign Office on Tuesday as the government announced a raft of new sanctions on individuals, companies, and others supporting the government of President Vladimir V. Putin of Russia.

Graham Phillips, 43, a pro-Kremlin blogger who was born in Nottingham, England, moved to Ukraine more than a decade ago and has spent the last several years recording and promoting videos from the country, amassing hundreds of thousands of followers to a YouTube account that has praised the Russian invasion. He worked briefly as a freelancer for the Russian state-owned television network RT, which many Western governments have accused of being a tool of the Kremlin and of spreading disinformation.

The Foreign Office, in announcing the freezing of Mr. Philip’s assets, characterized him as “a video blogger who has produced and published media content that supports and promotes actions and policies which destabilize Ukraine and undermine or threaten the territorial integrity, sovereignty, or independence of Ukraine.”

Mr. Phillips said in an email that he had been given no prior warning of the decision and questioned the legality of the measures.

“Please can someone explain to me how a British person can be put on a British sanctions list without any opportunity to defend himself, or any actual charges against him, just because the U.K. government don’t like his work?” Mr. Phillips wrote.

The move to punish Mr. Phillips came as Britain’s Foreign Office announced a raft of new sanctions on Tuesday directed at a number of people for supporting Mr. Putin’s regime, including Russian-installed officials in the eastern Luhansk and Donetsk regions.

Others on the expanded list included the justice minister and deputy justice minister of Russia, two nephews of oligarchs, and some Syrian citizens who the Foreign Office asserted were “undermining Ukrainian territorial integrity” by recruiting mercenaries in Syria.

Britain has sanctioned more than 1,000 people and 100 businesses since the Russian invasion of Ukraine began in February.

Mr. Phillips, who moved to Ukraine in 2010, was an English teacher for a time and wrote extensively about his experience in the country including detailing his own exploits in brothels, and writing about sex tourism in posts that have since been deleted.

When the Maidan protest movement over Ukraine’s future direction began in 2013, he began documenting the scenes, and, despite his inexperience, threw himself into making videos and filing reports on social media of the conflict, amassing a large following.

By 2014, he became a freelancer for RT. He has praised the Russian annexation of Crimea and regularly has voiced support for pro-Russian separatists in the country’s east, framing his videos as counterpoints to the Western narrative.

Since the full-scale Russian invasion of Ukraine began in February, Mr. Phillips has been documenting the war from the Russian side. This spring, Mr. Phillips interviewed and posted a video of Aiden Aslin, a British man who joined the Ukrainian military in Mariupol and then was captured by Russian forces.

Speaking in Parliament after the video was posted, Robert Jenrick, the lawmaker who represents Mr. Aslin’s constituency, said the interview was a “flagrant breach” of the Geneva Conventions, which bans broadcasting the questioning of prisoners of war.

Mr. Jenrick also said Mr. Phillips was “in danger of prosecution for war crimes.” Prime Minister Boris Johnson later said he “echoed the sentiments about those who broadcast propaganda messages.” The clip was later removed.