Ukrainian President Petro Poroshenko ordered a unilateral cease-fire Friday to give pro-Russia separatists in the east of the country a chance to lay down their arms in exchange for amnesty.

Speaking during his first visit as president to the troubled region, Poroshenko cautioned that the one-week truce won’t stop government forces from responding to any aggression.

“In case of an armed attack on the Ukrainian units or civilians, our servicemen will open fire,” Poroshenko was quoted as saying in a statement issued by his office.

The announcement was the first step in a plan that Poroshenko hopes will bring peace to southeastern Ukraine, where gunmen allied with Russia have seized government buildings and declared the Donetsk and Luhansk regions independent.

Other steps envisaged under the plan include early local and parliamentary elections, decentralization of some political authority to the regions and protection for the language rights of the many Russian-speakers who live there.

In return, the Ukrainian government is asking for the return of seized government facilities, the departure of Russian and Ukrainian mercenaries, and the establishment of a six-mile buffer zone along the border between the two countries.

Prominent separatists leaders rejected the plan as soon as it was announced Wednesday, saying they would discuss peace only when the government withdrew its forces and military hardware from the Donetsk and Luhansk regions.

The crisis in the area dates to March, when Russian President Vladimir Putin sent troops into Ukraine's Crimea area and later annexed it. Under pressure from Western sanctions, Putin has not openly supported appeals from the separatists in southeastern Ukraine to join their territory to Russia. But he has maintained a heavy troop presence along the border.

The Kremlin dismissed Poroshenko’s gesture Friday, saying in a statement quoted by Russia’s ITAR-Tass news agency that it looked like “this is not an invitation to peace and talks but an ultimatum to Ukraine’s southeastern militiamen to lay down arms.”

“The key element is yet lacking — a proposal to start talks,” the statement said.

Poroshenko made the announcement during a meeting with residents in the town of Sviatohirsk, in the Donetsk region. He emphasized that his cease-fire order, which took effect at 10 p.m. Friday, would remain in effect until 10 a.m. June 27, according to news reports.

Dmitry Tymchuk, a Ukrainian defense expert, said it was a serious attempt to resolve the crisis with minimal casualties. But he noted on his Facebook page that tanks had within the previous 24 hours crossed into Ukraine from Russia.

Ukraine accuses Russia of allowing such vehicles and other heavy weaponry used by the separatists to cross the border unhindered.

“Today the militants have at least six Grad missile systems – enough to create a local Armageddon,” wrote Tymchuk, who heads the Kiev-based Center for Military and Political Research.

Meanwhile, Russia accused Ukrainian forces of firing at one of its border checkpoints, causing material damage and injuring a customs officer.

“We are talking about a direct provocation,” said a statement published on the Russian Foreign Ministry website. “How can this correlate with the cease-fire declared by the Kiev authorities today?”

Times staff writers Loiko reported from Moscow and Zavis from Los Angeles.

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