Russia and Ukraine appeared to be heading for a tense stand-off on Tuesday night after Kiev threatened to close the border to an aid convoy that it fears could be a "Trojan Horse" for Russian intervention in the civil war.

A column of 262 lorries, which Russian officials say is packed with 2,000 tons of aid, left a military base near Moscow on Tuesday morning and is due to arrive at the Ukrainian border near the city of Kharkiv early on Wednesday.

But Ukrainian officials said the convoy would only be allowed to cross if it falls under the supervision of the International Committee of the Red Cross (ICRC).

How Russia might react if Ukraine refuses to admit the aid is unclear. Western leaders have warned that the Kremlin could use such a scenario as a pretext for direct military intervention in Ukraine.

"This convoy is not a certified convoy – it is not certified by the International Committee of the Red Cross," said Andriy Lysenko, a spokesman for Ukraine's National Security and Defence Council. "No military structures have the right to escort humanitarian aid convoys, especially into another state."