Ukrainian government forces were tightening the noose on pro-Russian separatists, shelling rocked Donetsk and sending frightened residents rushing for cover. It was not immediately clear if the artillery was fired by government or rebel forces.
Two shells landed 660ft 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.
The attack came as 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.
The 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.
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 the operation may become a covert military intervention by Moscow to prop up the rebels who appear on the verge of defeat.
In other developments, Russian President Vladimir Putin said he had signed off on establishing a Russian military task force in Crimea, which Moscow annexed from Ukraine, while on a visit to the Black Sea peninsula but said the presence would not be too heavy or costly.
In Kiev, the leader of Ukraine's populist Radical Party was nearly knocked out in a punch-up in parliament after he accused a fellow deputy of ignoring the plight of soldiers fighting in east Ukraine.
Oleh Lyashko staggered and appeared stunned after being punched by Oleksandr Shevchenko, whom he had called a "pot-bellied fatty".