(AP) -- Ukrainian President Petro Poroshenko ordered his forces to cease fire Friday and halt military operations for seven days against pro-Russia separatists in the country's east -- the first step in what he hoped is a concrete plan to end the conflict that has cost more than 350 lives.

Poroshenko, speaking during his first trip as president to the troubled east, said troops would still return fire if attacked.

"The forces of the anti-terrorist operation will halt military action starting today and through June 27," Poroshenko was cited as saying by the Interior Ministry on its website.

"Combat action will only be of retaliatory character if rebels attack our forces," he added.

He made announcement while speaking with residents in the town of Sviatohirsk in the Donetsk region. Refugees from the rebel-held town of Slovyansk where some of the worst fighting has taken place were also at the meeting.

Separatists in the Donetsk and Luhansk regions have declared independence from his government in Kiev. Rebel leaders have dismissed the plan and it remains to be seen to what extent they would comply.

Poroshenko has said a short cease-fire will give separatists time to lay down their arms and leave the country. Other steps include joint security patrols, new local and parliamentary elections, steps to protect language rights of the many Russian speakers in the area, and a jobs program.

On his visit, Poroshenko also visited the Monastery of the Holy Dormition near Syvatohirsk, an ancient Orthodox Christian monastery on the banks of the Seversky Donets river.

Earlier in the day, seven Ukrainian troops were killed in overnight fighting in the restive east as clashes between government forces and pro-Russia rebels flared ahead of the cease-fire.

Separatists were operating tanks in the region, a particular sore point for Ukraine, which accuses Russia of letting the vehicles and other heavy weaponry cross the border.

Russian President Vladimir Putin has voiced concern about the Ukrainian military operation against the rebels but has resisted both the rebels' pleas to join Russia and repeated calls from Russian nationalists for Putin to send troops into Ukraine. NATO reported Thursday, however, that Russia was resuming a military buildup at the Ukrainian border.

Vladislav Seleznev, spokesman for Ukrainian forces in the east, said in addition to the deaths, 30 troops were injured in fighting near the village of Yampil in the Donetsk region.

An Associated Press reporter saw pro-Russia fighters moving in a column with two tanks and three armored personnel carriers near the town of Yanakiyeve in the direction of Horlivka in the separatist Donetsk region. The tanks flew small flags of a pro-Russia militia but otherwise had no markings. The fighters declined to say what they were doing.

At the border crossing near Izvaryne in the separatist Luhansk region, an AP reporter saw a line of 100 or more cars waiting for hours to cross from Ukraine into Russia as people fled the unrest. Some of the cars were piled high with possessions. The United Nations said earlier this week that 34,000 people had been displaced by the fighting.

One car had a sign saying "children" on the windshield. A man named Sergei, who would not give his last name for fear of retaliation, said "people are simply leaving everything and trying to escape the war."

Poroshenko discussed the details of his peace plan on the phone Thursday with Putin, and his office says he emphasized the need for introducing effective border controls and quickly releasing hostages seized by the rebels.

Putin's spokesman, Dmitry Peskov, said Russian officials were surprised at Western expressions of concern over the renewed troop buildup, saying it was merely a previously announced measure to tighten border controls.

"This is not a matter of some sort of concentration of forces, but of the strengthening of border controls of the Russian Federation," Peskov was quoted as saying by the Itar-TASS news agency.

But a senior NATO military officer told The Associated Press in Brussels that the Russians are issuing misleading statements to cover their troop movements -- something they had also done in Crimea, along the border with Ukraine and now in eastern Ukraine. He spoke on condition of anonymity because he was not authorized to reveal NATO information.

Separately, Putin's foreign policy aide, Yuri Ushakov, said the Russian president is committed to dialogue on Ukraine and is planning to have a phone conversation with U.S. President Barack Obama in the coming days.

Ushakov also mentioned that Putin, on a visit to Austria next week, would be meeting with the chairman of the Organization for Security and Cooperation in Europe to discuss Poroshenko's peace plan.

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Nataliya Vasilyeva contributed from Moscow. John-Thor Dahlburg contributed from Brussels.