MOSCOW (AFP) - A convoy of nearly 300 trucks carrying what Russia says is humanitarian aid for victims of fighting in eastern Ukraine moved slowly towards the border on Wednesday despite concerns by Kiev and the West over the shipment, Russian officials said.

But Kiev again insisted it would not allow the convoy on its territory.

"No humanitarian convoy of Putin's will be allowed to cross the territory of the Kharkiv region," Ukraine's interior minister Arsen Avakov wrote on Facebook. "Provocation by the cynical aggressor will not be permitted on our territory."

Around 280 trucks are carrying more than 1,800 tonnes of "humanitarian supplies", including medical equipment, baby food, sleeping bags, and electric generators, according to Russian media.

President Vladimir Putin has justified sending the aid due to the "catastrophic" situation in the besieged rebel strongholds of Lugansk and Donetsk, where officials have warned of a looming humanitarian disaster because of shortages of food, water and power.

But there are concerns by Kiev and the West that Moscow could use the operation as a cover for sending in troops.

Russian media said the shipment had passed through the city of Voronezh on Wednesday, which would put it less than 300km from the border crossing at Shebekino, where the foreign ministry said the aid would enter Ukraine.

A Rossiya TV report from Voronezh said the convoy had over 500km to travel, and at an average speed of 60 kilometres an hour it would arrive at the border only in the evening.

"It's a long drive and a bit tough, but how can we not help our Slav brothers," one of the drivers of the white trucks said.

Kiev has said the trucks would be stopped at the border for any aid to be unloaded and transported into conflict-torn eastern Ukraine with the help of the International Committee of the Red Cross.

Russian Foreign Minister Sergei Lavrov said Tuesday that an agreement had been reached for the trucks to be inspected by Ukrainian authorities before continuing on with ICRC and Ukrainian representatives on board.

But Ukraine, which has accused Moscow of supplying the pro-Russian separatists with weapons, said no final agreement had been reached with the ICRC.

"I can say that Lavrov's statement is not true. Talks between the Red Cross and Russia are still continuing," said a source close to Ukrainian authorities.