As a controversial Russian convoy remains parked near Ukraine's border, two British reporters have claimed they have witnessed Russian military vehicles entering Ukraine.
In the first confirmed sighting of such an incident by Western journalists, Telegraph and Guardian reporters at the scene have claimed that a column of armoured vehicles and military trucks crossed the border from Russia into Ukraine on Thursday night.
Kiev, NATO and Western governments have long accused Russia of filtering arms and men across the border to fuel the separatist insurgency in Ukraine’s Donetsk and Luhansk regions, but such an incident has never before been witnessed by Western journalists.
A separate convoy - which Moscow claims is carrying aid - remains parked near Ukraine's border, still awaiting permission to travel to rebel-held cities in Ukraine's east, where shells have reportedly hit the centre of Donetsk for the first time.
Ukraine fears the "aid" convoy may carry military supplies for the pro-Russian rebels in a "kind of Trojan centipede," as the Guardian has put it, and has insisted that it be independently checked. Russia has dismissed the claims as "absurd."
Andriy Lysenko, a spokesman for Ukraine's National Security and Defence Council, said that if no independent checks took place "movement of the convoy will be blocked with all the forces available".
But Red Cross official Laurent Corbaz, in Kiev to discuss the convoy, said the Red Cross had a "strictly humanitarian role" and that "the delivery of aid should not be politicised".
Vladimir Putin, Russia's president, has said Moscow wants "to stop bloodshed in Ukraine as soon as possible".
However, The Guardian reporter on the ground with the convoy said: "The hundreds of men driving the trucks in the convoy were all dressed in identical khaki T-shirts, shorts and caps, and there was certainly something military about their bearing."
"But, with their easy manner, lack of discipline and in some cases physiques that hinted more at beer halls than special forces training grounds, the "little brown men" of the aid convoy are clearly not the highly trained elite troops used in the annexation of Crimea," The Guardian's Shaun Walker added.
Mr Walker said the trucks "do indeed appear to contain humanitarian aid… Nevertheless, Kiev's concern about the convoy, with its thinly disguised military undertones, is understandable."
Russia's aid convoy is aimed at Luhansk, where the Telegraph reports "residents have been without electricity and running water for several weeks, homes have been destroyed by artillery and mortar fire and food supplies are dwindling."
Ukraine is now sending its own 75-lorry aid convoy to the east, as heavy fighting continued on Thursday, with intense artillery shelling in both Luhansk and Donetsk.
The conflict in Ukraine, which has claimed more than 2,000 lives, has intensified in recent weeks.
While Russia's government has consistently denied arming or training pro-Russian rebels, the British journalists have now reported witnessing vehicles, including both armoured personal carriers and soft-skinned lorries, crossing into Ukraine at an obscure border crossing near Donetsk shortly before 10pm local time.
"The convoy, which included at least 23 vehicles, appeared to be waiting until sunset near a refugee camp just outside Donetsk, before moving towards the crossing without turning off headlights or making any other attempt to conceal itself," The Telegraph reported.
The Guardian's Mr Walker reported the same, saying "after pausing by the side of the road until nightfall, the convoy crossed into Ukrainian territory, using a rough dirt track and clearly crossing through a gap in a barbed wire fence that demarcates the border."
"The trucks are unlikely to represent a full-scale official Russian invasion, and it was unclear how far they planned to travel inside Ukrainian territory and how long they would stay. But it was incontrovertible evidence of what Ukraine has long claimed – that Russian troops are active inside its borders," he added.
The armoured column, he said, "appeared to be further evidence of Russia's incursions, which the Kremlin has repeatedly denied."