Ukraine President Petro Poroshenko has said that Russian military vehicles, which had allegedly crossed into the country during the night, have been destroyed by Kiev's forces.
A statement was published on Poroshenko's website which said that the Ukrainian leader held a telephone conversation with British Prime Minister David Cameron.
The pair reportedly spoke about emerging reports from Western journalists that Russian Armoured Personnel Carriers (APCs) were crossing into Ukraine near a Russian humanitarian convoy, destined for Ukraine's restive eastern regions.
"The president informed that the given information was trustworthy and confirmed because the majority of the machines had been eliminated by Ukrainian artillery at night," the statement said.
Russia had earlier denied reports that its troops had entered into Ukrainian territory, saying that the suspected armoured units were patrolling the border to "prevent the infiltration of armed people on the territory of the Russian federation".
"In this regard, information on a group of Russian soldiers crossing the Russian-Ukrainian border is not true," a Russian official told RIA Novosti.
An aid convoy of more than 200 white trucks has parked just before the joint Ukrainian-Russian border and its suspected destination is either the eastern regions of Donetsk and Luhansk, where there is a large pro-Russian rebel presence.
UN agencies estimate that more than 2,000 people have been killed in the fighting between the pro-Russian rebels and the Ukrainian military since April.
The downing of Malaysia Airlines flight MH17, suspected of being shot down by the rebels killing 298 passengers and crew, has again put the spotlight on the ex-Soviet state and Moscow's relationship with the separatists in eastern Ukraine.