Clashes broke out Sunday outside the main rebel-held city in eastern Ukraine, throwing the freshly forged ceasefire agreement between government troops and Russian-backed separatists into further doubt.

At least two houses blazed in the rural village of Spartak, which lies just north of Donetsk and adjacent to the airport, after they were hit by fire. A man whose house was struck by a shell said rebels had fired from a spot nearby, which appeared to have provoked a retaliatory attack from Ukrainian government troops. This pattern has been regularly observed in the nearly five-month-long military confrontation.

A group of rebel fighters in the village danced and drank Sunday morning in celebration after what they said was a successful assault on a Ukrainian military encampment in the vicinity. One said their group had captured eight government troops, although none of these captives could be seen.

The fighter, who provided only the nom de guerre Khokhol, freely acknowledged that the ceasefire was not being respected by either side.

"There was mortar shelling around 20 minutes ago here in Spartak," he said. "There is no ceasefire for anyone."

The truce signed on Friday appeared to be holding for much of the following day, but was shattered late Saturday by shelling on the outskirts of the southeastern port town of Mariupol, where Ukrainian troops retain defensive lines against the rebels. The city council said Sunday that one civilian was killed there and a serviceman wounded.

Mariupol is located on the coast of the Sea of Azov, 115 kilometres south of Donetsk. Rebels recently opened a new front on the coast, leading to fears that they were trying to secure a land corridor between Russia and the Crimean Peninsula, which Russia annexed in March.

'Disregard for civilian lives'

Amnesty International on Sunday condemned all those engaged in the grinding conflict that according to UN estimates has claimed at least 2,600 civilian lives and forced hundreds of thousands out of their homes.

"All sides in this conflict have shown disregard for civilian lives and are blatantly violating their international obligations," Amnesty International Secretary General Salil Shetty said in a statement.

Blasts powerful enough to be heard in downtown Donetsk could be heard coming from the direction of the airport early Sunday morning. The terminal, which has now been rendered little more than a burned-out husk, has been under the control of government troops since May and has come under unremitting attacks from Russian-backed separatist forces since then.

A local woman puts out the fire at her burning house after shelling in Donetsk, eastern Ukraine, Sunday, Sept. 7, 2014. (Sergei Grits/Associated Press)

A rebel statement said Ukrainian forces fired on their positions in six locations on Saturday, including near the Donetsk airport, and several rebels were killed.

In nearby Spartak, resident Anastasia Ivanusenko, who has moved to Donetsk to escape the most intense fighting, learned her house had been destroyed Sunday as she was coming to pick up some basic items for her child.

"I have a little baby and we are temporarily living in a dormitory. We wanted to get the stroller, some warm clothes for the child," she said, quietly sobbing on a bench across the road from her burning home. "There was no way to get into the house."

Conflicting claims over NATO weapons

Meanwhile, a senior aide to Ukraine's President Petro Poroshenko said Sunday that Kyiv had reached agreement during the NATO summit in Wales on the provision of weapons and military advisers from five member states of the alliance.

"At the NATO summit agreements were reached on the provision of military advisers and supplies of modern armaments from the United States, France, Italy, Poland and Norway," the aide, Yuri Lytsenko, said on his Facebook page.

A woman reacts after seeing the damages done to her house after returning home in Yasinuvata, on the outskirts of Donetsk, after a tepid ceasefire took effect this weekend. (Francisco Leong/AFP/Getty Images)

He gave no further details and it was not immediately possible to confirm his statement. NATO officials have said the alliance will not send weapons to Ukraine, which is not a member state, but they have also said individual allies may choose to do so.

However, three of those five swiftly denied making any such pledge.

Asked about Lytsenko's comments, defence ministry officials in Italy, Poland and Norway denied plans to provide arms.

"This news is incorrect. Italy, along with other EU and NATO countries, is preparing a package of non-lethal military aid such as bullet-proof vests and helmets for Ukraine," an Italian defence ministry official told Reuters.

Ukraine, Russia, the Kremlin-backed separatists and the Organization for Security and Cooperation in Europe signed the ceasefire deal in the Belarusian capital, Minsk, on Friday evening in an effort to end the bloodshed. The negotiators agreed on the withdrawal of all heavy weaponry, the release of all prisoners and the delivery of humanitarian aid to devastated cities in eastern Ukraine.

The 12-point agreement, published Sunday by the OSCE, also obliges Kyiv to give greater powers to the separatist Donetsk and Luhansk regions and calls for local elections to be held in those Russian-speaking regions.

Western leaders voiced skepticism over Russia's commitment to the deal. A previous 10-day ceasefire, which each side repeatedly accused the other of violating, yielded few results at the negotiating table.