KIEV, Ukraine (AP) — Both government troops and pro-Russian rebels began withdrawing heavy artillery in the east of the country, Ukrainian officials said Monday, a significant step toward implementing an effective cease-fire in the region.

Col. Andriy Lysenko, spokesman for Ukraine’s National Security and Defense Council, said Kiev’s forces had started withdrawing from frontline positions. He said the rebels had also begun their withdrawal of heavy artillery, although it was “not as massive as we expected.”