KIEV Ukrainian President Petro Poroshenko said on Tuesday pro-Russian separatists in the east had violated a ceasefire with overnight attacks that killed one government soldier.
Rebels and Ukrainian forces have both vowed to observe a week-long ceasefire until June 27, but the government has reported rebels shooting at military checkpoints.
"Unfortunately there were violations of the ceasefire from the other side. Last night there were another eight cases, one soldier was killed, seven were wounded," the president's press service quoted Poroshenko as saying during a meeting with German Foreign Minister Frank-Walter Steinmeier.
Rebel militia, using grenade-launchers and mortar, attacked a military post near the rebel-held town of Slaviansk and used small arms in an assault on another post towards the border with Russia, Vladyslav Seleznyov, a spokesman for the Kiev government's "anti-terrorist" operation, said earlier.
He said Ukrainian government forces had not been involved in any military action, in line with the ceasefire announced by Poroshenko last Friday.
Separatist leaders in two main areas of Ukraine's east on Monday night agreed to a truce until the morning of June 27, raising the first real prospect of an end to hostilities since rebellions erupted in the east in April.
The rebels, who have declared "people's republics" and have said they want to join Russia, began their ceasefire after talks involving a former Ukrainian president, Moscow's envoy to Kiev and a high-ranking representative of the OSCE security and rights organisation.
Poroshenko's ceasefire is part of his peace plan to end a pro-Russia insurgency in areas near the border with Russia which threatens to dismember the ex-Soviet republic.
Russia annexed Ukraine's Crimean peninsula earlier this year after street protests in Kiev ousted the Moscow-backed Viktor Yanukovich from power.
Poroshenko's plan, which offers a safety "corridor" back to Russia for pro-Russian fighters who lay down their arms, has secured the backing of Western governments and qualified support from Russian President Vladimir Putin who has urged Kiev to hold talks with the separatist leaders.
The next step in contacts between the two sides is not clear, though it seems likely the rebels may use the break in hostilities to press demands for federalisation of Ukraine - something which Kiev refuses because it sees it as likely to lead to the country breaking up.