"In accordance with agreements concluded with the Ukrainian side, three Ukrainian ships ... are being towed from the port of Kerch to an approved transfer point," border officials with the Russian secret service told the Interfax news agency.
The transfer was to take place on Monday, they added.
The TV channel Crimea 24 released footage of the three Ukrainian boats being towed by the Russian coastguard across the Kerch Strait.
The ships are seen passing under the Crimea bridge spanning the strait, built by Moscow to link Russia to the Crimean Peninsula, annexed in 2014.
In November last year, Russia seized the two Ukrainian gunboats and a tugboat as they headed through the Kerch Strait, a narrow waterway giving access to the Sea of Azov that is used by Ukraine and Russia.
Twenty-four Ukrainian sailors taken prisoner at the time returned to Ukraine in September as part of an exchange.
On Friday, the French presidency announced a summit involving France, Germany, Russia and Ukraine in Paris on Dec. 9 to discuss ways to resolve the wider conflict in eastern Ukraine.
The summit was made possible by "major advances" since Volodymyr Zelensky was elected president of Ukraine in late April, the French presidency said.
Kremlin advisor Yuri Yushakov however did not give a date for the summit in a Russian public television broadcast on Sunday. He said only that it was "still under discussion, but certainly this year."
It was not clear when the interview was recorded.
Since coming to power, comedian-turned-president Zelensky has sought to revive the peace process to end a five-year-old separatist conflict in eastern Ukraine, which has claimed 13,000 lives.
Since October, the Ukrainian army and Russian-backed separatists in eastern Ukraine have been pulling back from key front-line areas of the conflict there, a precondition for the summit to take place.