A pair of soldiers captured by Ukrainian government forces this week admitted they were active members of the Russian military, an independent monitoring group said Thursday. If confirmed, their confession would contradict the Russian government’s repeated denials of direct military involvement in the eastern Ukraine conflict between government forces and pro-Moscow separatist rebels.

Ukrainian soldiers captured the two men, identified as Capt. Yevgeny Yerofeyev and Sgt. Aleksander Aleksandrov, somewhere in eastern Ukraine on May 16. The men were taken to a hospital in the Ukrainian capital of Kiev, where they were interviewed by the Organization for Security and Co-operation in Europe, a monitoring group active in the region since the conflict began last year.

“Both individuals claimed that they were members of the unit of the Armed Forces of the Russian Federation. They claimed that they were on a reconnaissance mission. They were armed but had no orders to attack,” the OSCE said in a report on its findings, according to Agence France-Presse.

“One of them said he had received orders from his military unit to go to Ukraine; he was to ‘rotate’ after three months. Both of them said they had been to Ukraine ‘on missions’ before,” the report added.

Russian authorities have yet to directly respond to the OSCE’s report, but the Russian Defense Ministry previously denied the captured men were active members of the Russian army, the New York Times reports. Russian President Vladimir Putin has said in the past that any Russians captured in eastern Ukraine were “volunteers” who participate in the conflict of their own accord, AFP notes.

“We are completely certain and can state that these are citizens and servicemen of the Russian Federation,” a top Ukrainian government official said at a press conference Monday, according to Reuters. Ukraine has accused the two soldiers of “terrorist acts” against the Ukrainian people and has vowed to prosecute the men unless they deliver a full confession in open court.

Ukraine’s pro-West government, along with members of the European Union and the NATO military alliance, have accused Russia on several occasions of providing direct military support and weaponry to rebels active in eastern Ukraine. More than 6,000 people have died in the conflict since last year, but a shaky ceasefire agreement signed between Kiev and the separatists last February has limited hostilities.

Late last year, the European Union enacted sanctions against Russia as punishment for its annexation of the formerly Ukrainian territory of Crimea in March 2014, as well as for its apparent involvement in the eastern Ukraine conflict. The Kremlin has denied any involvement in the fighting.