Clashes between government forces and rebel fighters have killed 74 civilians over the last three days in east Ukraine's war-torn Donetsk region.

"Over the past three days, 74 residents of the region were killed and another 116 were wounded as a result of fighting," the Donetsk region's health authorities said in a statement. 

Earlier, pro-Russian separatists said heavy shelling hit several neighbourhoods around the rebel stronghold of Donetsk in eastern Ukraine where government forces are trying to tighten their grip.

There was no information on casualties.

It comes after President Vladimir Putin said Russia would stand up for itself but not at the cost of confrontation with the outside world, a conciliatory note after months of tough rhetoric over the crisis in Ukraine.

Mr Putin was speaking to Russian ministers and members of parliament in Crimea, the Ukrainian region annexed by Russia this year.

The tone of Mr Putin's comments was low-key and he avoided the kind of barbs that he has previously directed at Western countries during the crisis, which has dragged East-West relations to their lowest ebb since the Cold War.

European countries and the United States allege that Russia is supplying arms to separatists in eastern Ukraine.

Meanwhile, a Russian aid convoy left the southwestern city of Voronezh in the early hours of this morning and has been seen advancing towards the Ukrainian border.

Ukraine described Russia's dispatch of an aid convoy as a cynical act designed to fan a pro-Russian rebellion.

The Ukrainian government had declared that the convoy would not be allowed to pass.

However, a presidential spokesman later suggested a compromise might be found, bringing it under the control of the International Committee of the Red Cross (ICRC).

A senior ICRC official is due to travel to Kiev and Moscow today for talks on the delivery of the aid.

Laurent Corbaz, head of ICRC Operations for Europe and Central Asia, will stress the independent aid agency's "strictly humanitarian role" and that "the delivery of aid should not be politicised", spokeswoman Anastasia Isyuk said.

"The question of border crossing procedures and customs clearance (for the aid convoy) still have to be clarified between the two sides," Ms Isyuk said.

The convoy of 260 heavy trucks left the Moscow region on Tuesday and travelled about 500km to Voronezh.

There it stopped at an air base behind high fences.

Russia said any suggestion of a link between the convoy and an invasion plan was absurd.

Mr Putin has said his country should not "fence itself off from the outside world" despite the deterioration in East-West relations.

Mr Putin said the ongoing trade war with the United States and Europe did not mean Russia "should break ties with partners. But we should also not let them treat us with disdain".

The United Nations has put the overall death toll among Ukrainian forces, rebels and civilians at more than 2,000 since the beginning of the conflict in April.

Meanwhile, Igor Strelkov, the leader of the pro-Russian separatist rebels in Ukraine's Luhansk region announced his resignation this morning, saying he was injured and could not carry on in his role.

He is the second senior rebel to quit in the space of seven days.

Mr Strelkov is to be replaced by Vladimir Kononov.

Russian state-run broadcaster Rossiya 24 broadcast the statement by Valery Bolotov, head of the self-proclaimed Luhansk People's Republic.