German Chancellor Angela Merkel and French President Emmanuel Macron demanded Friday that Russia release Ukrainian sailors it captured along with their ships last month in the Kerch Strait, which links the Black Sea with the Azov Sea.

Moscow accused the 24 sailors of illegally crossing the Russian border. Ukraine said Russia captured the two small gunboats and one tugboat illegally and accused Moscow of military aggression.

"We demand safe, free and unimpeded transit for all ships through the Kerch Strait and the immediate and unconditional release of all illegally detained Ukrainian seafarers," Merkel and Macron said in a joint statement.

"They too should be able to celebrate the upcoming festivities with their families," they added.

Following the capture of the sailors and their vessels, Kiev has urged its Western allies to consider further sanctions against Moscow. Russia in its turn has accused Ukraine of plotting with the West to provoke a crisis.

Merkel and Macron added: "The human rights situation in Crimea, which was annexed by Russia in violation of international law, and the use of military force by Russia in the Straits of Kerch and abusive controls in the Sea of ​​Azov are also a source of great concern to us."