Ukrainian soldiers man a checkpoint outside the town of Amvrosiivka, eastern Ukraine, close to the Russian border, on June 5, 2014. (AP Photo/Vadim Ghirda)

Kiev, AP—Ukraine on Tuesday said its forces had captured 10 Russian soldiers in an eastern region where the Ukrainian troops are fighting pro-Russia separatists.

The Facebook page for the anti-rebel operation—which includes the military, the national guard and Interior Ministry forces—said the soldiers are from a Russian paratrooper division and were captured on Monday in the area of Amvrosiivka, near the Russian border in the Donetsk region.

The posting did not give details of how the capture took place. It posted videos of five men it said were among the captives, one of whom said the soldiers had been told they were being mobilized to take part in military exercises.

Russian news agencies quoted an unnamed source in the Russian Defense Ministry as saying the soldiers were patrolling the border area and probably crossed the border inadvertently.

Russia reportedly has tens of thousands of troops positioned in areas near the Ukrainian border, leading to persistent concerns that Russia could be preparing an invasion.

On Monday, Ukraine said 10 tanks and two armored vehicles belonging to the Russian military crossed into southeastern Ukraine bearing the flags of the rebel Donetsk People’s Republic. Ukraine also claimed that Russia fired artillery in the direction of the city of Novoazovsk in the far southeast.

Russia consistently denies allegations from Kiev and Western countries that it is supporting or directing the rebels and that it fires artillery into Ukraine.