A Russian convoy of 262 trucks packed with humanitarian aid is approaching the Ukrainian border amid fears that it might escalate the already tense situation in the war-ravaged east of the country.

The aid convoy was expected on Wednesday at the volatile Ukraine's border where pro-Russian forces and Ukrainian troops are engaged in fierce battles.

Russian media say some 2,000 tons of aid, from baby food to sleeping bags, was en route to east Ukraine, where some 1,300 people have been killed in fighting between pro-Russians and government forces.

Ukraine, however, on Tuesday pledged to deny entry to the Russian convoy, saying the mission could be a ploy to help pro-Kremlin forces.

"We will not consider the possibility of any movement of the Russian column on the territory of Ukraine," Deputy Head of Ukraine's Presidential Administration Valeriy Chaly said on Tuesday.

The United States and its European allies are now supporting Ukraine's plans to stop the convoy at the border.

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

Meanwhile, French President Francois Hollande expressed his concern over Russia's unilateral mission in Ukraine in a telephone conversation with his Russian counterpart Vladimir Putin.

A humanitarian operation "could only take place on Ukrainian territory if the national Ukrainian authorities gave their consent, both in terms of the format of the mission and on how it would be carried out," Hollande said.

Forces from the new Ukrainian government have been closing in on pro-Russian strongholds in the east over the past few days.