Ukraine says some of its sailors detained for illegally crossing the Russian border in the Crimean peninsula last week, have now been sent to prison in the capital Moscow.

Russian authorities arrested a group of 24 Ukrainian sailors and seized their three gunboats on Sunday after Russia accused them all of having deliberately trespassed into its territorial waters in the Sea of Azov.

Earlier this week, a Russian court in Crimea ordered the detained sailors and the vessels to be remained in pre-trial detention for two months—until January 25, 2019.

Dzhemil Temishev, one of the attorneys of the detained sailors wrote in a facebook post on Thursday that some of the sailors “are being taken to Moscow's Lefortovo prison.”

Another attorney, Emine Avamilyeva, said they were "taken by plane" to Moscow.

The sailors are charged with illegal border crossing by a group of individuals acting in collusion, or by an organized group, or with the use of or the threat to use violence, according to lawyer Aider Azamatov, who said they face up to six years in prison if convicted.

While Kiev has denounced the Russian action as "illegal," Moscow said it “acted in strict accordance with the law, both domestic and international.”

Tensions, already high between Kiev and Moscow since some four year ago, entered a new phase following Sunday’s incident in the Sea of Azov – a strategic ocean route linked to the Black Sea by the narrow Strait of Kerch where Russia has built a bridge to link the Crimean Peninsula with the mainland.

Tensions escalated earlier this year after Ukraine detained two Russian ships for port calls on Crimea — a former Ukrainian territory which rejoined Russia in a 2014 referendum.

The move prompted Russia to increase patrols off its Azov coast to guarantee free navigation by Russian ships. 

The recent incident risks pushing the two countries towards a wider conflict and is likely to renew Western calls for more sanctions against Moscow.

Russian President Vladimir Putin accused his Ukrainian counterpart Petro Poroshenko of orchestrating the naval “provocation” in the Black Sea to bolster his popularity ratings ahead of next year’s presidential election.

Moscow also said the United States is encouraging provocation between Russia and Ukraine

Turkey to play mediator role

Turkish President Recep Teyyip Erdogan said on Thursday that Ankara could play a mediation role to ease tensions between Moscow and kiev, saying he has “discussed this with both sides.”

"Both Mr Putin and Mr Poroshenko [the Ukrainian president] in our talks made requests,” said Erdogan refereeing to his telephone conversation with both presidents on Wednesday.

“We will convey the (Ukrainian) demands to Mr Putin in our meeting in Argentina," he said, adding that the issue would also be discussed in a meeting with US President Donald Trump in in the Argentine capital, Buenos Aires.

Erdogan made the remarks to reporter before heading to the G20 summit in the South American country.

The Turkish government is also working closely with Moscow on the Syria conflict and is also purchasing Russian S-400 missile air defense systems.

Meanwhile, UN Secretary-General Antonio Guterres, who is also in Buenos Aires, said on Thursday that he was "greatly concerned" about the escalation of tension between Russia and Ukraine, calling on "both parties to exercise maximum restraint and to take steps without delay to contain this incident and reduce tensions," according to his spokesman.

The latest hostilities between Moscow and Keiv has also affected the planned meeting between Trump and Putin on the sidelines of the G20 summit over security issues, arms control, and issues in the Middle East and Ukraine.

Trump abruptly called off the meeting over the escalation of tensions between Moscow and Kiev. 

The Russian government spokesman Dmitry Peskov expressed regret over the Trump’s decision saying that Putin "is ready to have contacts with his American counterpart."

“This means that discussion of important issues on the international and bilateral agenda will be postponed indefinitely,” Peskov added.