The Russian soldiers that were caught in eastern Ukraine crossed the border "by accident," Russia's military said according to the BBC.

Ukraine said on Tuesday it captured 10 Russian troops near the village of Dzerkalne, south of the rebel stronghold city of Donetsk, after they crossed its border with Russia.

A Russian defense ministry official told the Russian news agency RIA Novosti that the soldiers, said to be paratroopers, "really did participate in a patrol of a section of the Russian-Ukrainian border, crossed it by accident on an unmarked section, and as far as we understand showed no resistance to the armed forces of Ukraine when they were detained."

Ukrainian troops are always crossing the border into Russia, the ministry official added.

"We did not give much publicity to that. We just returned all those willing to return to Ukrainian territory at safe places."

But Ukraine, which has long suspected Moscow of aiding the pro-Russian separatists in the nearly five-month war, does not believe Russia's explanation.

"This wasn't a mistake, but a special mission they were carrying out," Ukrainian military spokesman Andriy Lysenko said according to the BBC.

The Russian paratroopers were captured a day after Ukraine's military said Russian tanks crossed the border and were stopped near the eastern city of Novoazovsk. Ukraine also said a group of Russian soldiers disguised as rebel fighters crossed the border.

Ukrainian officials said Tuesday's incident is irrefutable evidence of Russia's involvement in the uprising.

"Officially they are at exercises in various corners of Russia," Ukrainian Defense Minister Valeriy Geletey said, Sky News reported. "In reality, they are participating in military aggression against Ukraine and their families know nothing about their true fate."

Over 2,000 people have died since the conflict between pro-Russian insurgents and Ukrainian forces began in April, according to the BBC. The fighting was sparked when Russia annexed the Ukrainian peninsula Crimea following the ousting of former president Viktor Yanukovych.