Kiev, Aug 23 (IANS): As German Chancellor Angela Merkel arrived in the Ukrainian capital, about 100 lorries from an unauthorised Russian aid convoy crossed back over the border from eastern Ukraine, BBC reported Saturday citing officials.

The convoy was returning from Luhansk city, held by pro-Russian separatists who have been fighting Ukrainian government forces.

International monitors, based in the border region, said that some of the vehicles have crossed back into Russia, a development confirmed by Russian news agencies.

Meanwhile, Merkel, who described the convoy as a "dangerous escalation" Friday, arrived in the Ukrainian capital Kiev for talks.

At least 220 trucks drove into Ukraine Friday, headed for the rebel-held Luhansk city, affected by weeks of fighting between Ukrainian forces and pro-Russian rebels.

Though Kremlin officials say the vehicles are only carrying generators, food and drink, western officials fear the convoy could be part of a military intervention.

The lorries had been waiting at the border for a week, while Russia, the Ukrainian government, and the Red Cross tried to come to an agreement on their passage. The Russians said they could not wait any longer, owing to the worsening humanitarian situation in eastern Ukraine, held by pro-Russian separatists.

Four months of fighting in the region has left over 2,000 people dead while more than 330,000 have fled their homes.

The White House Friday warned Russia that sending an aid convoy into eastern Ukraine without Kiev's approval would incur "additional consequences", Xinhua reported.

NATO Secretary General Anders Fogh Rasmussen has also condemned the unauthorised Russian convoy.

The European Union has deplored as illegal the Russian decision to send humanitarian aid into Ukrainian territory without an International Committee of the Red Cross (ICRC) escort or the Ukrainian government's consent. It described the Russian convoy into Ukraine as a clear violation of Ukrainian borders.