Artillery shells hit close to the centre of Ukraine’s separatist-held city of Donetsk for the first time yesterday, killing at least one person, as a large Russian aid convoy rumbled towards the border.

With Ukrainian government forces tightening the noose on pro-Russian separatists, shelling rocked Donetsk, sending frightened residents rushing for cover, witnesses said.

It was not immediately clear if the artillery was fired by government or rebel forces.

Two shells landed 200 metres from the Park Inn Radisson, one of the city’s main hotels, shattering windows. The blasts opened up a yawning hole on the third floor of an apartment block and left a broad crater on the pavement.

Nearby, a body covered by a sheet lay stretched out on the blood-stained ground.

The blasts opened up a yawning hole in an apartment block

A huge Russian convoy carrying 2,000 tonnes of water, baby food and other humanitarian aid drove through southern Russia towards the frontier, while Kiev repeated it could not enter until Ukrainian authorities had cleared its cargo.

A leading separatist military leader in east Ukraine, Igor Strelkov, also resigned, the separatists’ self-proclaimed Donetsk Republic said on its website.

A Russian convoy of trucks carrying humanitarian aid for Ukraine. Photo: Maxim Shemetov/ Reuters

It said Vladimir Kononov would replace Strelkov as the new military commander. Strelkov's resignation was a third change at top of the rebel leadership of the past week.

The pro-Western Kiev government says the humanitarian crisis is partly of Moscow’s making and has denounced the dispatch of aid as an act of cynicism. It is also fearful that the operation could become a covert military intervention by Moscow to prop up the rebels who appear on the verge of defeat.

Moscow, which denies charges – also voiced by the West – of giving the rebels heavy weapons, has dismissed as “absurd” suggestions it could use the convoy as a cover for invasion.

By yesterday evening, the convoy had stopped near Kamensk-Shakhtinsky and one of the drivers told Reuters it would be heading to the crossing point at Izvarine, which is held by the Ukrainian rebels.

If this were the case, Ukrainian border guards and customs officers would be unable to conduct proper formalities and make the checks they say are needed on the cargo.

“The cargo will all the same have to be looked at by Ukrainian border guards and transferred to representatives of the Red Cross,” said military spokesman Andriy Lysenko yesterday. It was not immediately clear how this could happen.

The caravan of 280 trucks left the Moscow region on Tuesday, looking to take aid to Luhansk region, in eastern Ukraine, where the main city is held by the separatists.

Even if the convoy were to enter Ukraine via Izvarine, it would not be able to get to Luhansk city without encountering government troops at Novosvitlivka, a settlement which Kiev forces took only yesterday.

“Ukrainian forces have closed the last possibility for road communications between Luhansk and other territories which are controlled by Russian mercenaries in particular Izvarine,” Lysenko said.

Relief agencies say people living in Luhansk and in Donetsk, the region’s main industrial hub, are facing shortages of water, food and electricity after four-months of conflict in which the UN say more than 2,000 people have been killed.

Ukrainian troops have been slowly encircling Donetsk, which had a peace-time population of nearly a million.