A Russian convoy carrying "humanitarian aid" has turned away from its route towards a confrontation with government officials at the Ukrainian border - and is now heading straight for rebel-held areas.
The huge deployment of around 260 trucks towards eastern Ukraine has sparked international fears of a Trojan Horse-style invasion, as last night the Ukrainian president accused Moscow of potentially planning a "direct invasion of Ukrainian territory under the guise of delivering humanitarian aid".
Moscow said that the column of white spray-painted Kamaz trucks, which left a military depot outside the Russian capital early on Tuesday morning, was full of vital supplies ranging from baby food to sleeping bags.
It had been parked since late on Tuesday at an army base in the southern city of Voronezh while Russian and Ukrainian diplomats argued over how the aid might be received.
Video: Ukraine says no to Russian convoy
By taking the road south towards the rebel-held city of Luhansk, the convoy now appears intent on ignoring a tentative agreement which would have seen it cross the government-controlled border at Kharkiv, where it could be inspected by the international Red Cross.
The border at Luhansk is in the heart of the disputed region and largely rebel-held. Speaking on Tuesday, even the pro-Russian separatist leader Andrei Purgin said he did not expect the aid to be sent there directly.
The Red Cross has said that while it is aware of the existence of the Russian convoy, it has no knowledge of where it is headed and "no information" at all about its contents.
Kiev, the West and much of Europe have blamed Russia for providing arms and expertise in support of the rebels in eastern Ukraine, who have been battling government forces since April.
Ukraine crisis: Russian 'aid' convoy
Ukraine crisis: Russian 'aid' convoy
1/11 Ukraine crisis
Drivers of the first trucks of the Russian aid convoy parked in the city of Luhansk on 22 August
2/11 Ukraine crisis
An employee inspects the contents of a truck with Russian humanitarian aid in Mariupol, Ukraine on 22 August 2014
3/11 Ukraine crisis
The convoy nearing the border before it parked at a camp in Russia
4/11 Ukraine crisis
Russian convoy carrying humanitarian aid for residents in rebel eastern Ukrainian regions moving along a road in the city of Voronezh, about 530 km from Moscow, Russia
5/11 Ukraine crisis
An Ukrainian border guard checks passing cars at a checkpoint of Pletnyovka, Kharkiv region on Ukraine-Russia border, where Russian humanitarian convoy is to cross the border
6/11 Ukraine crisis
Ukrainian border guards stand at the Ukrainian-Russian border crossing
7/11 Ukraine crisis
Trucks of a Russian convoy carrying humanitarian aid for Ukraine are parked at the military air base outside Voronezh
8/11 Ukraine crisis
Drivers of a Russian convoy of trucks carrying humanitarian aid for Ukraine take a rest on a side of a road near the city of Yelets
9/11 Ukraine crisis
An Ukrainian soldier stands guard at a checkpoint of Pletnyovka, Kharkiv region on Ukraine-Russia border, where Russian humanitarian convoy is to cross the border
10/11 Ukraine crisis
A Russian convoy carrying humanitarian aid for residents in rebel eastern Ukrainian regions moves along a road about 50 km from Voronezh, Russia, 14 August 2014. The convoy continues to advance through Russian territory after a one-day stop in Voronezh in full coordination with and under the aegis of the Red Cross, according to Russian authorities
11/11 Ukraine crisis
The Russian convoy carrying humanitarian aid in the Voronezh region of Russia en route to Ukraine
The conflict has killed more than 2,080 people, according to the UN's human rights office in Geneva, and left many more desperately short of food, water and medical aid.
Dmitry Peskov, a spokesperson for the Russian President Vladimir Putin, insisted late on Wednesday that the operation was proceeding in full cooperation with the Red Cross - but did not comment on the route the convoy would take.