KIEV, Ukraine — Warring parties in Ukraine took a major stride toward quelling unrest in the country’s east Thursday with the declared start of a supervised withdrawal of heavy weapons from the front line.

While announcing the pullback, Ukraine’s Defense Ministry warned that it would revise arms withdrawal plans in the event of any attacks. “Ukrainian troops are in a state of total readiness to defend the country,” it said in a statement.

The pullback was supposed to have started over a week ago under a peace deal agreed upon this month by the leaders of Russia and Ukraine to end the fighting in eastern Ukraine that has killed nearly 5,800 people since April. The intensity of fighting has declined notably in recent days, despite daily charges by both sides that the other is violating the Feb. 15 cease-fire.

Rebels in the Donetsk and Luhansk regions insist they have spent the last few days drawing back their heavy weapons – a claim not yet verified by independent observers. Donetsk separatist leader Alexander Zakharchenko mirrored Ukrainian willingness to immediately resort to combat if provoked.

“Military equipment will be returned to their positions. Any attacks on our cities and villages will be nipped in the bud,” he said.

The press office for Ukrainian military operations in the east said that government forces Thursday started moving 100 mm anti-tank guns back the 16-mile minimum stipulated by the peace deal. Journalists in the southeastern government-held port city of Mariupol on Thursday saw weapons matching that description heading away from the front.

Near Olenivka, a town south of the rebel-held stronghold of Donetsk, journalists saw rebel forces moving at least six 120 mm self-propelled howitzers from the front line.