Britain has summoned Moscow's ambassador to London over reports of a Russian military incursion across its border with Ukraine, the Foreign Office said today.
Alexander Yakovenko was summoned "to clarify reports of Russian military incursion into Ukraine and continued buildup of equipment on border," the ministry said in a tweet.
Ukraine said today it had destroyed part of a Russian military convoy that crossed onto its territory, sending tensions over the situation in the east of the country soaring.
British Prime Minister David Cameron also spoke to Ukrainian President Petro Poroshenko on a telephone call today.
A spokesman for Cameron's Downing Street office said after the call that the prime minister had "expressed grave concerns at reports of Russian military vehicles crossing the border."
The spokesman added that both sides had agreed humanitarian aid should be delivered through the International Committee of the Red Cross.
"Both leaders also agreed on finding a political solution to de-escalate the situation and the prime minister welcomed President Poroshenko's readiness to engage with Russia and other partners to achieve this," the spokesman added.
"Russia needs to demonstrate the same willingness to find a peaceful resolution to the conflict.