Fighting flared between Ukrainian government forces and Russian-backed separatists in two separate parts of eastern Ukraine overnight with several civilians killed by shelling, Ukrainian police and separatist sources said on Monday.
The clashes, near Mariupol in the southeast and at Gorlivka, a rebel-held town, formed part of an upsurge in violence which put further strain on a fragile ceasefire between the two sides.
Regional police in Mariupol, a port city on the Sea of Azov, said at least one man and a young woman were killed when rebels shelled the town of Sartan, about 20 km (12 miles) away on Sunday. Several people, including a 10-year-old girl, were taken to hospital with wounds.
"On one street there were five houses which had been really badly damaged by shell fragments. One house had a well-tended garden with vines and a vegetable patch. But the house had been wrecked by shells and I saw an enormous pool of blood," a local news photographer, Mykola Ryabchenko, told Reuters by telephone.
The separatist website, DAN, said at least three people had been killed and four wounded as a result of government shelling of Gorlivka, a regular frontline hot spot northeast of the main rebel stronghold of Donetsk.
There was no immediate government confirmation of this report.
"They were using heavy weapons. We have three men dead. Another four have various injuries," DAN quoted the separatist mayor of the town as saying.
The upsurge in fighting weighed on the Russian rouble on Monday. It touched a six-month low against the dollar, dropping 1 percent.
It has also drawn expressions of concern among Western governments, who see a ceasefire and tentative peace agreement worked out in Minsk, Belarus, as still the best chance of ending the separatist rebellion in eastern Ukraine.
Many artillery guns, tanks and other heavy weapons have been withdrawn by both sides under the terms of the Minsk agreement in February, but deaths occur regularly in sporadic outbursts of fighting.
More than 6,500 people have been killed in the conflict which erupted in April 2014 after Russia annexed Crimea, in reaction to the fall of a Moscow-backed president in Kiev, and threw its support behind separatists in the east.
U.S. Secretary of State John Kerry last week expressed "grave concern" to Russian Foreign Minister Sergei Lavrov over the rise in separatist attacks and urged an immediate ceasefire, the State Department said.
In a newspaper interview, German Foreign Minister Frank-Walter Steinmeier said the situation was explosive and he urged both parties in the conflict to come together quickly to prevent a spiral in violence.