Ukraine may block Russian humanitarian aid convoy
Ukrainian officials have set conditions for receiving Russian aid in the east, after a huge convoy of food and medicine set off from outside Moscow.
Security council spokesman Andriy Lysenko said aid should pass through a government-controlled border post and be accompanied by Red Cross officials.
There are Western concerns that Russia is using humanitarian assistance as a pretext to invade eastern Ukraine.
At least 1,500 have died since Ukraine sent troops against pro-Russia rebels.
The fighting in the Donetsk and Luhansk regions since mid-April has displaced hundreds of thousands of people, many of whom have fled to Russia.
The Red Cross says it still needs more security guarantees and information about the aid convoy.
Taken by surprise
Almost 300 lorries of humanitarian aid left the Moscow area bound for Luhansk on Tuesday morning.
Russian TV showed the cargo, said to include hundreds of tonnes of grain, baby food and medicine, which will go to civilians trapped by fighting in the area held by pro-Russia rebels.
Media reports said the cargo left from a point south-west of Moscow. It is expected to arrive at the Ukrainian border in the next two days.
"The convoy will deliver to the residents of eastern Ukraine about 2,000 tonnes of humanitarian cargo, collected by the residents of Moscow city and region," Moscow region officials said.
But Mr Lysenko said Ukraine had three conditions for receiving the aid:
- That it should pass through a border post controlled by Ukrainian government guards
- That it should be accompanied by Red Cross representatives
- That a decision should be made about the amount being sent, its destination and route.
Another Ukrainian official, Valery Chaly, said Ukraine would not allow access to a convoy accompanied by the Russian military or Emergencies Ministry.
Analysis: The BBC's David Stern, Kiev
As the 280-truck Russian aid convoy makes its way to the Ukrainian border, the questions are building.
Where will its cargo be passed on to Ukrainian and international officials? What exactly is contained among its 2,000 tonnes of aid? And how exactly will the transfer be made?
Ukrainian officials insist that the Russian trucks will stop at the border, where their freight will be passed onto vehicles controlled by the Red Cross.
Still, the high level of interest - and emotion - that the aid delivery has unleashed, points to a level of uncertainty that not all is as simple as it appears.
Russian President Vladimir Putin on Monday announced the Russian humanitarian mission in co-operation with the International Committee of the Red Cross (ICRC).
The ICRC has acknowledged the situation in eastern Ukraine is critical, with thousands of people reported to be without access to water, electricity and medical aid.
On Tuesday, the organisation said it was not involved in the Russian mission as some issues needed clarification and security guarantees from all sides were required.
But it said it had agreed in principle to such an operation and suggested it could get involved if the clarification it had asked for was received.
War in Ukraine: the human cost
Casualties: At least 1,543 people have been killed in the east since mid-April, including civilians, the military and members of the armed groups, the UN said on 8 August. Some 4,396 have been confirmed wounded "but the real number is likely to be much higher". Ukraine said on 11 August that 468 of its soldiers had been killed. The rebels have reported losing at least 800 fighters.
Refugees: Nearly 300,000 people have been forced from their homes this year. More than 117,000 are displaced inside Ukraine, 87% of them from the Donetsk and Luhansk regions, while a further 168,000 have crossed into Russia. Source: UN refugee agency
On Monday, Western officials warned that Russia could be planning military operations in eastern Ukraine, using humanitarian aid as a cover.
"We see the Russians developing the narrative and the pretext for such an operation under the guise of a humanitarian operation, and we see a military build-up that could be used to conduct such illegal military operations in Ukraine," said Nato Secretary-General Anders Fogh Rasmussen.
Responding to news of the convoy's departure, French Foreign Minister Laurent Fabius warned that the mission could be a way for the Russian military to install itself in eastern Ukraine and present the world with a fait accompli.
Ukraine has reported in recent days that Russia has massed 45,000 troops on its border.
However, Kremlin spokesman Dmitry Peskov described the idea of using the aid convoy as an excuse for military action as "absurd" and said the mission was purely humanitarian and non-military.
Advances by government troops in recent weeks have put pressure on the rebel-held cities of Donetsk and Luhansk, leaving the latter in particular virtually cut off.
On Tuesday, Ukrainian President Petro Poroshenko said his forces had recaptured the strategically important town of Vuhlehirsk.
The fighting has also prevented a full investigation of the MH17 air disaster on 17 July, in which 298 people died.
It is strongly suspected that the plane was shot down by pro-Russian rebels. Russia and the separatists have blamed the Ukrainian military.
Speaking on Tuesday, US Secretary of State John Kerry said he hoped to find a way for Ukraine to work with Russia to help bring about a formal investigation into the crash.