Kiev: US-led military exercises began in Ukraine on Monday after a day of deadly fighting between government forces and pro-Russian rebels in the restive east that has piled pressure on a shaky ten-day-old truce.

Local officials said six civilians died during heavy shelling around the rebel stronghold of Donetsk on Sunday, with Kiev accusing the separatists of jeopardising the truce by intensifying attacks against government positions.

It is the highest civilian toll since the ceasefire was signed on September 5, although a number of Ukrainian servicemen have also been reported killed over the past ten days.

Soldiers from 15 nations including the United States began military exercises dubbed “Rapid Trident 14” near the western city of Lviv, about 1,000 kilometres from the conflict in Donetsk.

The United States was expected to send around 200 troops, the first such deployment since the pro-Moscow uprising erupted across eastern Ukraine in April.

Defence Minister Valeriy Geletey said on Sunday that Nato member states were sending weapons to Ukraine, although this has been previously been denied.

A Nato official said he could neither confirm nor deny the claim “as any such delivery would be done on a bilateral basis”.

Ukraine’s new leaders have nevertheless announced they want to begin taking steps to join the Western military alliance, a red line for Kiev’s former Soviet masters in Moscow.

The conflict in Ukraine’s vital industrial heartland and Moscow’s annexation of Crimea sent ties between Russia and the West plunging to their lowest point since the Cold War.

The warring sides signed up to a 12-point ceasefire after talks in the Belarussian capital Minsk — the first truce backed by both Kiev and Moscow — but there have been reports of violations almost daily.

‘Concern’

President Petro Poroshenko and German Chancellor Angela Merkel “expressed concern” about the breaches in a telephone call late on Sunday, his office said.

It also said Merkel backed Poroshenko’s plans to introduce legislation in parliament this week, offering limited self-rule for the eastern regions that form the economic backbone of Ukraine, a key provision of the truce.

“The terrorist actions are threatening the realisation of the Ukrainian president’s peace plan,” said Volodymyr Polyovy, a spokesman for the national security and defence council in Kiev.

He also took aim at comments by two rebel leaders who both signed the truce deal but who declared on Sunday they were mere “observers” at the Minsk talks.

Sunday’s fighting appeared to be heaviest near Donetsk airport where the Ukrainian military said it had driven back an assault by insurgent fighters on Friday.

But the separatists accused Kiev’s forces of failing to halt fire.

“From our side, nobody is shooting but they are breaking the rules, everybody in the world knows it,” said a rebel commander defending a checkpoint near a village south of Donetsk.

The ceasefire is seen as a first step in efforts to draw up a longer term peace deal to end a conflict that has cost more than 2,700 lives and sent at least half a million fleeing battered towns and cities across the east.

The truce halted a rebel surge across the southeast last month with the alleged support of Russian paratroopers and heavy weaponry, turning the tide against Ukrainian forces.

Nato and Kiev say at least 1,000 Russian soldiers and possibly many more remain on Ukrainian soil, with another 20,000 massed on the border.

The Kremlin has dismissed the claims as propaganda aimed at justifying Nato moves to bolster its forces in eastern Europe, saying some of its troops captured in Ukraine had accidentally strayed across the border.

Prime Minister Arseniy Yatsenyuk echoed deep Western suspicions about Moscow’s territorial ambitions when he accused President Vladimir Putin on Saturday of seeking to “eliminate” Ukraine as an independent country.

Poroshenko, keen to steer Ukraine further out of Russia’s orbit by strengthening ties with the West, meets President Barack Obama in the White House on Thursday, seeking to secure a “special status” with the United States.

Obama has rejected direct military involvement but unveiled tougher economic sanctions on Moscow that — together with similar EU measures — effectively lock Russia out of Western capital markets and hamstring its crucial oil industry.

Russian Foreign Minister Sergei Lavrov accused Washington of trying to use the crisis to “break economic ties between the EU and Russia”.

The punitive measures and an accompanying East-West trade war have left Russia’s economy facing possible recession, and the rouble tumbled again on Monday to a new low.