MOSCOW (Reuters) - Two Ukrainian navy captains being held in a Russian jail have refused to provide testimony because they consider themselves prisoners of war, their lawyers said on Wednesday.

FILE PHOTO: A detained Ukrainian serviceman and crew member of one of Ukrainian naval ships, which were recently seized by Russia's FSB security service, looks out of a minibus window outside a court building in Simferopol, Crimea November 28, 2018. REUTERS/Pavel Rebrov/File Photo

Russia seized three Ukrainian navy vessels and their combined crew of 24 last month off the coast of Russian-annexed Crimea and accused them of illegally entering Russian waters.

Ukraine has said Russia captured the two small gunboats and one tugboat illegally and accused Moscow of military aggression.

The United States and the European Union have called for the release of the sailors, who are in pretrial detention in Moscow.

Roman Mokryak, the commander of one of the gunboats, told Russian investigators he would not provide any information until his crew was released, his lawyer, Ilya Novikov, said on Wednesday.

“He believes he alone answers for what happens on board, that his crew carried out his orders and that they cannot be held to account,” Novikov wrote on Facebook.

Oleh Melnychuk, the captain of the tugboat, has also refused to testify, denying Moscow’s accusations and calling himself a prisoner of war, his lawyer Edem Semedlyayev wrote in a separate Facebook post on Wednesday.

No date has been set for the sailors’ trial.

Ukraine has said it fears Russia is preparing to attack it, citing an alleged military buildup along its border. Russia denies this and says Ukrainian President Petro Poroshenko is trying to whip up anti-Russian sentiment as part of an election campaign.

Russia annexed Ukraine’s Crimean peninsula in 2014 and backs separatists fighting Kiev’s forces in the east of the country.

In Washington, the Pentagon said Ukraine Navy Commander Admiral Ihor Voronchenko would be meeting with officials, including Chief of U.S. Naval Operations Admiral John Richardson, on Thursday and Friday.

“(Pentagon) leaders will reiterate the U.S. support for Ukraine’s sovereignty and territorial integrity within its internationally recognized borders, extending to its territorial waters, as well as the right of its vessels to traverse international waters,” Pentagon spokesman Eric Pahon told Reuters on Thursday.