Updated

Russian-backed rebels in eastern Ukraine say they have begun a large-scale pullback of heavy weapons in line with an international peace plan that aims to form a wide buffer zone between separatists' and Ukrainian forces' artillery.

The claim Tuesday by Eduard Basurin, a top rebel commander, could not immediately be confirmed. Michael Bociurkiw, a spokesman for the observer mission that is monitoring the fighting in eastern Ukraine, said he could not comment until receiving monitors' reports at the end of the day.

The peace plan that was signed Feb. 15 calls for heavy weapons to be pulled back by each side from the front line by 25 to 70 kilometers, depending on their caliber.

A rebel website cited Basurin as saying about 100 122-mm howitzers would be moved on Tuesday.