KIEV (AFP) - Ukraine's new coalition government made joining Nato a priority on Friday in a move likely to provoke fresh Russian anger as thousands gathered in Kiev to mark the first anniversary of protests which unleashed a year of turmoil.

A crowd of several thousand gathered in Kiev's Independence Square, known as Maidan, late Friday to remember the more than 100 protesters who died in demonstrations that started on Nov 21 last year.

Many mourners were draped in Ukrainian flags, while some cried and laid flowers in memory of the dead.

On a hectic day of politicking, Ukraine's leaders announced a new coalition following October elections which affirmed that joining the Nato military alliance would be a priority.

It agreed to pass a law by the end of the year confirming this intention.

Such a move threatens to further provoke Russia, which denies Western accusations that it is providing military support to pro-Moscow separatists in eastern Ukraine as part of a strategy to thwart the country's pro-Western course.

The five-party parliamentary coalition - which will have a big enough majority to make constitutional changes - features the groupings of President Petro Poroshenko, Prime Minister Arseniy Yatsenyuk and former premier Yulia Tymoshenko.

Poroshenko confirmed that pro-Western Yatsenyuk will keep his post to head the coalition government, which faces a mammoth task dealing with the gravest crisis in Ukraine's post-Soviet history.

US SAYS RUSSIA'S ROLE 'UNACCEPTABLE'

During a visit to Kiev on Friday, US Vice-President Joe Biden told Russia it faced paying an ever-higher price over its policies in its western neighbour.

Biden described as "unacceptable" the Kremlin's role in the crisis in eastern Ukraine, but stopped short of offering lethal military supplies to Kiev forces battling rebels in a seven-month conflict which has killed 4,300 people.

Hinting at possible new sanctions, he warned Russia had failed to fulfil its commitments under a September peace plan, adding: "So long as that continues, Russia will face rising costs, greater isolation."

As Biden met Poroshenko and Yatsenyuk, Kiev claimed that shelling was taking place from across the Russian border for the first time since a tattered ceasefire was signed in September.

Ukrainian military spokesman Andriy Lysenko said that in the past day, artillery had been fired at a border post in the Lugansk area from the direction of Manotsky in Russia's Rostov region.

Ukraine's government has for months urged the US to give it weapons and ammunition to fight pro-Moscow forces in the east.

Ministers had hoped Biden would use his visit to announce further US assistance for its forces but his office announced only US$23 million (S$30 million) to support justice reforms and food rations.

Before Biden's visit, Russia warned the US against arming Ukrainian forces. The secretary of its national security council, Nikolai Patrushev, said the conflict in eastern Ukraine "will grow" if that happened.

POROSHENKO HECKLED

Earlier on Independence Square, Poroshenko was heckled by relatives of the dead shouting "Shame!" over the authorities' failure to convict anyone over the deaths as he laid a candle at the shrines which surround the square.

Some protesters spoke of their cynicism at the current political system and warned that they could be forced to launch fresh protests over the widespread corruption and lack of political reforms in Ukraine.

"I have a sense of deja vu," said Yulia Demchuk, a 36-year-old lawyer.

"I have the feeling that I am still continuing the protest on Maidan but there is no inspiration now. There is disappointment as I can see that the authorities are not taking any steps to change anything."

Petro Runkiv, a 58-year-old civil engineer who took part in the protests, added: "Of course we are disappointed. Nothing changed.

"We need reforms and we are here to let our government know that we are ready for one more Maidan."

Meanwhile, the toll of dead and injured continued to rise in eastern Ukraine despite a ceasefire which has been repeatedly violated.

Almost 1,000 people have died in fighting since September, according to the United Nations.

Two Ukrainian soldiers and two civilians were killed in the region since Thursday, Ukrainian security officials said.