German Chancellor Angela Merkel warned that diplomacy aimed at resolving the crisis in Ukraine might not succeed.

At the Munich security conference on Saturday, Merkel said she was working towards securing peace in Europe with Russia. She also underlined her opposition to supplying lethal weapons to the Ukrainian government, according to an AP report.

Proposals will be discussed in a phone call Sunday with Russian President Vladimir Putin, Ukrainian President Petro Poroshenko and French President François Hollande.

The US is considering giving lethal weapons to Ukraine, an option opposed by European nations.

US Air Force General Philip Breedlove said he favoured aiding Ukrainian forces with weapons and equipment, rather than sending in troops.

"I don't think we should preclude out of hand the possibility of the military option," he said at the Munich conference, but added: "There is no conversation about boots on the ground."

However, Germany is against arming Ukrainian troops for fear of worsening the crisis.

"The problem is that I cannot imagine any situation in which improved equipment for the Ukrainian army leads to President Putin being so impressed that he believes he will lose militarily," she said. "I have to put it that bluntly."

"This conflict cannot be resolved by military means," Merkel said at the Munich Security Conference. "It is all the more important now to set out substantial steps that serve to fill with life the Minsk agreement."

Merkel said of the talks that "it is uncertain whether they will be successful, but it is from my point of view and that of the French president in any case worth making this attempt".

The German leader acknowledged that experience to date of agreements being violated on the ground has been "disillusioning".

However, gun battles and shelling are continuing on Saturday, with five civilians and five government soldiers killed in east Ukraine, according to government and pro-Russian rebel officials.

Missile fire on Saturday hit east Ukraine's battleground town of Debaltseve a day after a brief truce allowed hundreds of civilians to flee, government officials said. "In Debaltseve since 6am this morning rebels have been firing Grad rockets," said Kiev-loyal regional police chief Vyacheslav Abroskin.

More than 5,300 people have been killed since fighting began in April, according to the UN, with the death toll increasing, despite a ceasefire being declared on Friday. An AFP journalist in the rebel city of Donetsk said that the sounds of heavy explosion were reverberating around the town on Saturday.