Red Cross officials are in Kiev trying to negotiate its passage.Ukraine, which fears the convoy may carry military supplies for the rebels, insists it be independently checked.Meanwhile, two UK newspaper reporters said they had witnessed Russian military vehicles entering Ukraine.Journalists from the Guardian and the Telegraph said a column of more than 20 armoured personnel carriers with soldiers on board had crossed the border.Russia's government has consistently denied directly arming or training pro-Russian rebels, who sparked the conflict in April when they took control of several cities in eastern Ukraine.The conflict, which has claimed more than 2,000 lives, has intensified in recent weeks.On Thursday, there was heavy shelling in the rebel stronghold cities of Donetsk and Luhansk.And the rebels announced that their main military commander Igor Girkin - known as Strelkov - had resigned.'Strictly humanitarian'The humanitarian convoy of at least 260 lorries drove for nine hours on Thursday before parking in a field near the border.Russia dismissed as absurd claims that its convoy was a pretext to send military supplies to the rebels.But Ukraine insisted on an inspection by international monitors.Andriy Lysenko, a spokesman for Ukraine's National Security and Defence Council, said that if this did not happen, "movement of the convoy will be blocked with all the forces available".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".Red Cross spokeswoman Anastasia Isyuk said the convoy was "south of the city of Kamensk-Shakhtinski" and that the Red Cross had been in contact with the Russian representatives.She said there was still no agreement on the issues of border crossing procedures and customs clearance.The BBC's Steve Rosenberg, who has been following the convoy, says the key question now is what Russia will do next - if it takes the convoy across the border, it will be seen by the Ukrainian authorities as a major provocation.Ukraine is sending its own 75-lorry aid convoy to the east and Mr Corbaz said that too was being discussed in Kiev.The US has issued another warning to Russia.State department spokeswoman Marie Harf said: "We've made that very clear to the Russians that they should not move these trucks in, without taking all of the steps the Ukrainian government has outlined."Ceasefire callHeavy fighting continued on Thursday, with intense artillery shelling in both Luhansk and Donetsk.Ukrainian authorities said they had cut off Luhansk from other rebel-held areas after capturing the town of Novosvitlivka.Ms Harf said the US had "stressed the importance of showing restraint to minimise casualties among the civilian population".The Russian foreign ministry on Thursday called for an "urgent" ceasefire.Strelkov, file picThe loss of Strelkov, meanwhile, represents the third high-profile resignation of rebel leaders in the past week.In Donetsk, the rebels' political leader Alexander Borodai handed over to Alexander Zakharchenko.And Valery Bolotov, rebel commander in Luhansk, said he was temporarily handing over to Igor Plotnitskiy.Mr Borodai said reports that Strelkov, a Russian citizen, had been injured were "total rubbish".Some 2,086 people have been killed since the conflict in the east began in mid-April, more than half of them in the past two weeks, the UN says.The violence began when pro-Russian rebels seized government buildings and tried to declare independence.The military launched an operation to retake the east, and stepped up its activities in June.Russian President Vladimir Putin on Thursday visited Crimea, which Russia annexed from Ukraine in March in a move that drew international condemnation.Mr Putin said Russia's goal was "to stop bloodshed in Ukraine as soon as possible".He said Russia should not "fence itself off from the outside world" although he said Russia would "not allow anyone to treat us with arrogance".(BBC)Bakudaily.Az