At least six Ukrainian servicemen were killed in separatist attacks on Sunday in Ukraine's troubled eastern regions in a grim weekend marking the first anniversary of a rebellion against Kyiv's pro-Western rulers.
Four Ukrainian soldiers died when their vehicle was hit by a shell fired by the Russian-backed rebels as it drove across a bridge in the government-held town of Schastye, 170 kilometers (105 miles) northeast of the big regional center of Donetsk, regional police said.
In a separate incident less than an hour later, a landmine exploded under a military vehicle at Shyrokyne, east of the Sea of Azov city of Mariupol, killing two soldiers and injuring a third, a military spokesman said on the TV channel 112.
The new casualties, which followed the deaths of three Ukrainian servicemen in a landmine explosion on Saturday, put further strain on a tenuous cease-fire struck two months ago.
The conflict erupted a year ago this weekend when rebels opposed to a new pro-Western leadership in Kyiv and the ousting of a Moscow-backed president occupied state buildings in two big cities of Ukraine's Russian-speaking east, Donetsk and Luhansk.
More than 6,000 civilians, rebels and Ukrainian servicemen have been killed since then in a crisis in which Kyiv has accused its former Soviet master of arming and supporting the rebels and the West - backing Ukraine - has brought economic and financial sanctions against Russia.
The crisis has now reached stalemate with a cease-fire, brokered by Ukraine, Russia, Germany and France in mid-February still technically in force though deaths are reported almost daily among Ukrainian soldiers, civilians and rebels.
But large swaths of the industrialized east, including the cities of Donetsk and Luhansk, are under the control of the rebels and Kyiv fears they could be preparing to try to take Mariupol, a city of a half-million people.
Under an agreement reached in Minsk, Belarus, the warring sides have pulled back heavy military equipment to put their big guns out of range of each other and are working on extending the withdrawal to include tanks and smaller-caliber weapons.
But the status of the separatist-controlled regions, remains disputed, and the rebels appear unlikely to allow Ukrainian elections to be held there later this year.
Both sides accuse each other of violating the cease-fire agreed in Minsk despite the pull-back of heavy weapons.