Ukraine said on Friday that it destroyed part of a column of military vehicles that had crossed the border from Russia — a claim swiftly denied by Russia.
Ukrainian President Petro Poroshenko made the claim in a telephone call with British Prime Minister David Cameron: "The President...confirmed that the majority of the Russian military armored vehicles had been destroyed by the Ukrainian artillery at night."
The UK said it had summoned Russia's ambassador to explain, the BBC reported.
Late on Thursday, two reporters, including Shaun Walker of The Guardian stumbled upon a column of armored personnel carriers (APCs) that they witnessed cross the border from Russia into Ukraine.
Russia denied that its troops had entered Ukraine and said that additional border guards had been deployed to the area to "prevent the infiltration of armed people on the territory of the Russian federation," the Guardian reported. It said the unit operated only inside Russia: "In this regard, information on a group of Russian soldiers crossing the Russian-Ukrainian border is not true," RIA Novosti quoted an official as saying, the Guardian reported.
A Russian defense official, Igor Konashenkov, went further and said: "There is no Russian military column, that supposedly crossed the Russian-Ukrainian border either during the day or at night."
"Such statements, based on some sort of fantasies or, rather, on the assumptions of journalists, should not become a subject for the serious discussion between the top officials of any country," Konashenkov said in a statement, RIA-Novosti, a Russian newswire, reported.
Despite Russia's denial, the eyewitness reports of the incursion appeared to confirm what many had suspected for months — and what the Ukrainian government has claimed for months: that Russian military equipment was making regular incursions into East Ukraine. It was unclear whether the APCs were driven by Russian soldiers or the separatists they back in East Ukraine.
In Copenhagen, NATO Secretary General Anders Fogh Rasmussen confirmed the incursion but added: "What we have seen last night is the continuation of what we have seen for some time," the New York Times reported.
Reporters had been following a massive convoy that Russia says is filled with humanitarian aid destined for Ukraine when they saw the incursion.
The trucks remain stalled in Russia, the New York Times reported, and there were conflicting reports on whether Ukrainian border officials had been allowed to inspect their load, which Russia claims comprises food and other aid for civilians caught in Ukraine's civil strife.
The UN says the death toll in the conflict, raging for months, has doubled in the past two weeks, jumping from 1,129 dead on July 26 to 2,086 people dead by Aug. 10.