Ukraine says a soldier has been killed and five others wounded in separatist attacks in eastern Ukraine and that a rise in violence is threatening the region's delicate truce.

Col. Andriy Lysenko, presidential spokesman for the military operation against the separatists, said Wednesday that the casualties came amid 21 separatist violations of the cease-fire over the past day, including mortar attacks.

A cease-fire was agreed to in February, but did not appear to take real hold until the beginning of September, when both sides agreed to halt shooting on the first day of the new school year. They then agreed to pull back smaller-caliber artillery, bolstering an earlier heavy weapons pullback.

A top rebel official, Eduard Basurin, on Wednesday in turn accused Ukraine of returning heavy weapons to the region.