"There is reason to believe that Ukrainian special services were involved," a Russian Foreign Ministry spokesperson said.

Russia said it arrested a man suspected in the murder of a senior military official near Moscow and claimed that a car bomb had been activated remotely from Ukraine.

Russian authorities say the suspect in the killing of a Russian general in a car bomb explosion claimed he was paid by the Ukrainian Security Service as he pleaded guilty to terrorism charges

Russian President Vladimir Putin claimed his country has recaptured Kursk, the border region where Ukraine launched a surprise offensive last year, though Kyiv insists its troops are fiercely battling to preserve its foothold in the territory.