Ukraine's security service on Monday said its military in the war-torn east has captured 10 Russian paratroopers on Ukrainian soil and was questioning them as part of a criminal probe.
Soldiers from the 331st regiment of 98th airborne division based in central Russia were taken near the Ukrainian village of Dzerkalne, about 50 kilometres (30 miles) southeast of the rebel hub Donetsk, it said in a statement.
"Russian soldiers have been detained with personal documents and weapons," it said, adding: "Investigators opened a criminal probe into illegal border crossing by armed Russian citizens."
Ukraine's Defence Minister Valeriy Geletey said the soldiers had been captured on Monday -- hours before Ukrainian President Petro Poroshenko is due to meet Russian leader Vladimir Putin for the first time in months.
"Today Ukrainian armed forces captured many Russian soldiers," Geletey wrote on his Facebook page late Monday.
"Officially they are at exercises in various corners of Russia. In reality, they are participating in military aggression against Ukraine" and their families know nothing about their true fate, he said.
"I am addressing the relatives of Russian servicemen: find out immediately where your loved ones are. Take them out of Ukraine, where they are being forced to die," he added.
Kiev has long accused Moscow of stoking the separatist insurgency raging in its east but this is the first time Ukrainian authorities have claimed to take soldiers from Russia's regular army captive.
Ukraine's security service said the captured soldiers testified to having been sent to Russia's Rostov region, which borders Ukraine's restive Donetsk and Lugansk regions, but added that "only the officers knew that Russian hardware would be invading on Ukrainian territory".
On Thursday, officials said the Ukrainian army captured two vehicles and documents belonging to Russian paratroopers.
Moscow has repeatedly denied any involvement in the rebellion in Ukraine, calling all evidence fabrication.