A Russian court on Wednesday prolonged the detention of Ukrainian sailors captured last year near Crimea, in the midst of sensitive prisoner-swap talks between the two countries.  

Moscow's Lefortovsky district court ruled that 13 of the sailors must stay in detention for an extra three months until October 24. Another 11 were due to hear their fate later Wednesday.  

The Russian navy captured the Ukrainian sailors and their three vessels in the Kerch Strait, which links the Black Sea and the Sea of Azov, on November 25, 2018, after opening fire on them. Moscow accuses them of illegally entering Russian waters, something Kiev denies. 

Lawyer Nikolai Polozov, who heads the defense team, said Russia and Ukraine were negotiating a possible prisoner exchange. He declined to discuss any details.  

Ukraine's rights ombudsman Lyudmyla Denysova, who attended the hearing, confirmed that talks about the "release" of the sailors and other Ukrainians were underway.  

The Hamburg-based International Tribunal for the Law of the Sea said in May that Moscow should release the sailors immediately. The Kremlin rebuffed that call. 

Russian President Vladimir Putin said in June that the fate of the Ukrainian sailors must be linked to the release of Russian citizens held in Ukraine whom Moscow wants to see freed. 

Putin and Ukraine's new President Volodymyr Zelenskiy held their first telephone conversation last week and discussed settling the conflict in eastern Ukraine and the return of prisoners. 

Tensions escalated between Moscow and Kiev after Crimea was incorporated into Russia in March 2014 following a local referendum, which was rejected by Ukraine.

(With inputs from agencies)