About 300 US Army paratroopers have arrived in Ukraine for training exercises with national guard units, a move criticized by the Kremlin and eastern Ukraine's Russia-backed separatist rebels.

The troops, from the Italy-based 173rd Airborne Brigade, are to spend several weeks training a total of about 900 Ukrainian national guardsmen. The guardsmen are to come from units including the Azov Battalion, a far-right formation notorious for using an insignia used by many military units in Nazi Germany.

Though fighting has diminished substantially since a February cease-fire deal, clashes continue and each side accuses the other of wanting to resume the conflict.

On Friday, the UN Human Rights Commissioner's office said at least 6,116 people have been killed since the fighting broke out a year ago.