Ukraine's army chief of staff has listed for the first time some of the specific Russian military units alleged to be fighting against Kyiv alongside pro-Moscow rebels in eastern Ukraine.
Viktor Muzhenko, in an interview published by Ukraine's Defense Ministry on April 18, said, "Regular Russian army troops are still in Ukraine" despite a cease-fire agreement signed in February which ordered the withdrawal of foreign fighters from the front line.
Russia has repeatedly denied claims by Kyiv and the West that it is arming and sending troops to help separatists who have gained control of parts of the east.
Muzhenko named the Russian army's 15th Mechanized Infantry Brigade, the 8th Mechanized Infantry Brigade, the 331st Airborne Regiment, and the 98th Airborne Division.
He said he had "proof" that Russian regular troops had fought in three clashes in the east in February, including a fierce battle for the rail hub of Debaltseve, which is now controlled by the separatists.