Lorries from a Russian aid convoy are streaming into Ukraine without permission, after Russia accused Ukraine of unreasonable obstruction, BBC News reported.

Russia's foreign ministry said Ukraine had held up the convoy in order to pursue war against rebels in Luhansk, where the aid is destined. The International Committee of the Red Cross (ICRC) said it was "not part of that convoy in any way".

A Ukraine official said responsibility for the convoy rested on the Russians. Reports suggest the lorries are being escorted by pro-Russian activists.

"Our humanitarian aid convoy is starting to move towards Luhansk," the Russian foreign ministry said in a statement. It warned Ukraine not to take any action against the convoy without specifying the consequences.

Ukraine fears that the aid convoy of at least 260 lorries, which arrived at the border more than a week ago, is part of a broader Russian intervention in eastern Ukraine.

Russia denies accusations that it arms and trains the activists in the rebellion in Luhansk and the neighbouring region of Donetsk, where four months of fighting have left more than 2,000 people dead and has caused more than 330,000 people to flee their homes.

The activist-held city of Luhansk has been without running water, power and phone communications for 20 days as government forces hold it under siege.