Moscow's Lefortovo district court has extended the term of custody for all 24 captive Ukrainian sailors until 24 April.
It took the decision with regard to 20 Ukrainian sailors during closed sessions on 15 June and four others the next day.
The sailors once again declared themselves prisoners of war and refused to provide any information apart from their names and ranks.
Their lawyers plan to appeal the court rulings.
On 25 November, Russia attacked three Ukrainian naval ships in international waters off the Kerch Strait, damaging the vessels and injuring three Ukrainian sailors. It detained the crews and captured the vessels. All the 24 Ukrainian sailors declared themselves prisoners of war.
They have been arrested for two months for trespassing and are currently held in custody in Moscow.