Sergey Lavrov, Russia's foreign minister, has warned of a possible Ukraine offensive against pro-Moscow separatists in east Ukraine, following an upsurge in fighting that has left nine people, including at least seven civilians, dead.
"We are worried by the developments in recent days, which strongly recall preparation for more military actions," Lavrov told a news conference, accusing Kiev of breaking the terms of a ceasefire with rebels.
"It was like that in August last year when Ukrainian soldiers received the order to attack. It was like that in January of this year," Lavrov said.
Earlier on Monday, officials from both sides of the conflict reported that seven civilians had been killed in intense shelling by Ukrainian forces and pro-Russian rebels in the separatist east.
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"Two civilians - a man and a woman - were killed in overnight shelling in Sartana village," about two kilometres northeast of the government-held port of Mariupol, Volodymyr Kolesnyk, a spokesman for the local health department, told the AFP news agency.
Kolesnyk said that six more civilians were wounded and one man was killed in a Kiev-controlled village close to the rebels' de facto capital, Donetsk.
Meanwhile, pro-Russian separatist officials reported the deaths of four civilians in overnight bombardments, three of them in Donetsk.
On Saturday, Ukraine's army reported coming under the heaviest level of artillery and rocket fire since the two sides signed a February truce deal that has been repeatedly broken since.
Kiev's pro-Western forces have been fighting the rebels in recent days for control of a strategic highway linking Donetsk with Mariupol - the last major government-held city in the region.
Most of the highway is currently controlled by pro-Kiev units. Its capture would allow the separatist fighters to step up their stop-start campaign to capture Mariupol - a port city of nearly half a million people on the western edge of the loosely defined demilitarised zone.
Russia denies any links to the rebels and officially provides them only with political backing at negotiations and UN Security Council forums.
But both Kiev and its Western allies accuse the Kremlin of orchestrating and arming the uprising, in revenge for Ukraine's decision to pull out of Moscow's orbit and ally itself with the European Union.
The UN estimates the violence has killed more than 6,800 people since April 2014 and has driven at least 1.4 million from their homes.