Lugansk: Hundreds of pro-Russian gunmen struck a Ukrainian border guard camp with mortar and grenade launchers on Monday in one of the biggest offensives of an insurgency which Washington says is directed by Moscow.
The well-coordinated dawn raid involving rebel snipers perched on rooftops led to a day-long battle at the base on the southern edge of the separatists` stronghold city of Lugansk.
Kiev officials said at least five insurgents were killed and eight servicemen wounded.
An explosion also destroyed a regional administration building used as a headquarters by the rebels.
The separatist region`s self-declared "prime minister" Vasyl Nikitin told AFP he personally helped carry away four bodies, two civilians -- killed as they were walking in a park -- "one of our fighters and our minister of health".
He described the scene as "a hell", adding that the death toll could rise as there were others who were gravely wounded.
An AFP reporter saw fighters pull the body of one rebel sniper from the roof of a nine-storey apartment block building with his white shirt soaked in blood.
The border guard service said its forces and the rebels agreed to a 30-minute afternoon ceasefire so that both sides` wounded could be evacuated by ambulance.
A spokesman for Ukraine`s self-proclaimed "anti-terrorist operation" said the border guards eventually received air cover from fighter bombers that managed to destroy "two mortar crews of militants".
Russia`s foreign ministry angrily accused Kiev of "committing another crime against its own people".The clashes were an unwelcome reminder to president-elect Petro Poroshenko of the difficulty of keeping his May 25 election promise to save his crisis-hit country from disintegration and economic collapse.
The 48-year-old pro-Western chocolate baron had earlier on Monday won a surprise reprieve when Russia`s state gas firm Gazprom delayed a threatened cut in fuel shipments that would also impact large portions of Europe.
The European Commission announced Monday it will hold further talks with Ukraine and Russia "this week or next" on resolving their gas supply dispute after outlining a possible price regime to secure supplies to June 2015.
Moscow had threatened to halt all shipments to Ukraine -- a vital gas transit nation now seeking a closer alliance with the West -- from Tuesday in a repetition of interruptions that also hurt swathes of Europe in 2006 and 2009.
A visit to Kiev by US Assistant Secretary of Defence Derek Chollet marked another boost for Ukraine`s attempts to build global pressure against attempts by a part of its economically vital industrial east to join Russia.
Downing Street said British Prime Minister David Cameron would also press Russian President Vladimir Putin to take immediate steps to defuse Europe`s worst crisis in decades when the two meet on the sidelines of Friday`s D-Day commemorations in Normandy.
Putin did hold a private meeting on Monday with an ex-leader from the West -- former French president Nicolas Sarkozy, who was in Russia to attend a concert by his wife Carla Bruni in Moscow.
Dmitri Peskov, a spokesman for the Kremlin said the meeting "took place in Sochi," the Black Sea resort city, earlier Monday, adding that it was of a "private nature" and gave no further details.
But as for Putin`s first face-to-face with Poroshenko, a Kremlin spokesman said it "is not being worked upon" despite the new Ukrainian leader`s promise to arrange such talks in Normandy.
Russia instead submitted a draft resolution to the UN Security council on Monday for "aid corridors" to be opened up that would allow easier movement across its border into Ukraine.
"We want the Security Council to demand that no obstacles are put up to prevent the peaceful population from leaving the zones of military operations or to prevent the delivery of humanitarian aid to these zones," said Russian Foreign Minister Sergei Lavrov.
Kiev has accused Russia of using the aid corridor idea as a means to expand its influence in eastern Ukraine. US Treasury Secretary Jacob Lew said Washington was prepared to push for tougher economic sanctions against Russia at a G7 leading nations summit in Brussels on Thursday because Moscow was still trying to destabilise Ukraine.
"There is evidence that Russia continues to allow the free flow of weapons, funds, and fighters across its borders and President Putin`s next steps are still not clear," Lew said in a Washington address.
He added that US President Barack Obama "has given us the authority to take even more powerful action if Russia continues to support armed separatists in eastern Ukraine".
In another sign of Washington`s support for the Kiev government, the White House said Obama during his visit to Poland Wednesday would meet with Poroshenko, and US Vice President Joe Biden will attend his inauguration on Saturday.
NATO and Russia ambassadors also held a testy first meeting since the Crimea crisis that one Western official said involved a "very frank" exchange of views.
Monday`s discussion clearly showed "that there are fundamentally different views on this crisis, on its origins, on what is happening now and on how it should be resolved," alliance spokeswoman Oana Lungescu said after the Brussels talks.
Poroshenko -- a tycoon and political veteran who as foreign minister enjoyed good working relations with top Moscow officials -- is seeking a closer Western military alliance and distancing himself from Putin`s embrace.
The Pentagon`s Chollet said after talks with Ukraine`s acting defence minister that Washington was in discussions to provide $18 million (13 million euros) in military assistance.