KIEV, April 17 - The European Union and the United Nations on Monday expressed alarm over a spike in violence in east Ukraine that claimed 10 lives as Russia warned Kiev could be preparing a fresh offensive.

The single day death toll is the highest in over a month as government troops and pro-Moscow rebels accuse each other of gearing up for a renewed onslaught that would finish off an already tattered February truce, AFP reported.

"We really strongly condemn this escalation of fighting and we call all sides to cease it and to observe the ceasefire," European Commission spokeswoman Catherine Ray told journalists in Brussels.

UN Secretary-General Ban Ki-moon said he was "seriously alarmed" by the upsurge in violence, adding that the ongoing "ceasefire violations and the resulting loss of life are unacceptable".

Russia -- accused by Kiev and the West of sending troops and weapons across the border to fuel the insurgency -- turned the spotlight on Kiev, warning Ukraine could be readying for fresh fighting.

"We are concerned by the course of events in recent days which very strongly resembles the preparation for more military action," foreign minister Sergei Lavrov said.

Lavrov alleged that Ukraine's forces were intensifying their activities in Shyrokine, a flashpoint village 10 kilometers (six miles) from the government-held port of Mariupol.

Ukraine's foreign ministry, however, lashed out at the rebels and their alleged backer Moscow for the uptick in violence.

"Ukraine calls on Russia to take immediate measures to stop the escalation of the situation," the ministry said in a statement.

On the ground, Ukrainian officials reported the death of two soldiers and three civilians, while a rebel commander said five civilians were killed across the conflict zone in the latest surge in violence.

Volodymyr Kolesnyk, a spokesman for the local health department, told AFP that two civilians were killed in overnight shelling in Sartana village some two kilometers northeast of Mariupol.

An AFP journalist in the village saw dozens of buildings destroyed and the roof of one house ripped off.

Kiev's forces in recent days have been fighting the rebels for control of a strategic highway linking Donetsk with Mariupol – the biggest government-held city in the region.

Most of the road is currently controlled by pro-Kiev units. Its capture would allow the separatist militants to step up their stop-start campaign to capture Mariupol -- a port city of nearly half a million on the western edge of the loosely defined demilitarised zone.

Mariupol's port exports most of the breakaway east's industrial output and controlling it could be a step towards creating a land bridge between the separatist region and the Russian-annexed Crimea peninsula.

In a move that further angered Kiev, Russian President Vladimir Putin visited Crimea Monday to discuss the region's stuttering development under Moscow's rule.

Ukrainian President Petro Poroshenko described the visit as a "challenge to the civilized world.” (afp/ez)