Ukrainian troops have ceased fire in a fight against pro-Russian separatists as a first step in efforts to de-escalate the conflict in the country's east, days after rebel leaders rejected a peace process.
Petro Poroshenko, Ukraine's president, announced a week-long truce on Friday, but said the army would fight back in case of a separatist attack.
"The forces of the anti-terrorist operation will halt military action starting today and through June 27," Poroshenko was cited as saying in comments published on the Ukrainian Interior Ministry's website.
Shortly after the annoucement, the Kremlin was quoted by the Russian news agencies as saying that the truce declaration sounded more like an ultimatum.
Poroshenko said the ceasefire would give separatists time to lay down their arms and leave the country, to be followed by talks, new local elections and a jobs programme.
Poroshenko discussed the details of his peace plan on the phone on Thursday with Vladimir Putin, Russia's president, and his office says he emphasised the need for introducing effective border controls and quickly releasing hostages seized by the rebels.
Rebel leaders have dismissed the plan and it remains to be seen to what extent they would comply.
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 ceasefire.
Vladislav Seleznev, spokesman for Ukrainian forces in the east, said 30 troops were injured in fighting near the village of Yampil in the Donetsk region.
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.
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 on Thursday, however, that Russia was resuming a military build-up at the Ukrainian border.
Dmitry Peskov, Putin's spokesman, said Russian officials were surprised at Western expressions of concern over the renewed troop build-up, 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 a Russian news agency, Itar-TASS.
Separately, Yuri Ushakov, Putin's foreign policy aide, said Putin was committed to dialogue on Ukraine and was planning to have a phone conversation with US President Barack Obama in the coming days.