Russia on Thursday announced that it had opened a criminal case against a CNN correspondent and two Ukrainian reporters on charges of entering the country illegally while reporting on an incursion into the Kursk region by Ukraine’s armed forces.

The announcement brings to five the number of reporters facing similar charges. The Russian security service, the F.S.B., also brought a case against two Italian journalists last week. And the Foreign Ministry has said that further cases are under consideration, including against reporters from The Washington Post.

An F.S.B. statement identified the CNN reporter as Nick Paton Walsh, a British citizen who is a chief international security correspondent. It also named two reporters from Hromadske, an independent Ukrainian news organization: Olesya N. Borovik and Diana V. Butsko.

None of the three are based in Russia, and there appeared to be no immediate prospect of their detention there. The statement from the F.S.B. said that they would be placed on Russia’s wanted listed.

The Russian government’s actions seemed intended mostly to intimidate those reporting on its failure to prevent Ukrainian forces from seizing a large chunk of territory along the border. Ukraine has also long threatened to take action against reporters who file dispatches from Crimea, which Russia occupied in 2014, if they do not first seek a permit from the government in Kyiv.

Under Russian law, the maximum penalty for illegally crossing the border is four years in prison and a fine of several thousand dollars, according to the F.S.B. statement, which was quoted by the official news agency Tass.