London,U.K.: The US said that Russian military aircraft entered Ukrainian airspace amid rising tension in the east of the country and called it "dangerously destabilising" and "very provocative", a media report said on Saturday.
Russia has deployed thousands of troops along its border with Ukraine, BBC reported.
The statement came on Saturday as the group of G7 (US, UK, Canada, France, Germany, Italy and Japan) industrialised countries agreed to impose fresh sanctions on Russia over Ukraine.
"Given the urgency of securing the opportunity for a successful and peaceful democratic vote next month in Ukraine's presidential elections, we have committed to act urgently to intensify targeted sanctions and measures to increase the costs of Russia's actions," a joint statement from the G7 said.
"We have now agreed that we will move swiftly to impose additional sanctions on Russia," the statement added.
According to official reports, the US might impose the sanctions as early as Monday.
Pentagon spokesman Col Steven Warren on Friday said that Russian aircraft had entered Ukrainian airspace several times and asked Moscow to take immediate steps to de-escalate the situation.
Meanwhile, Ukraine's interior ministry said that armed protestors had seized seven representatives from the Organisation for Security and Co-operation in Europe (OSCE) as well as five Ukrainian army personnel and a bus driver.
Pro-Russian activists in Sloviansk confirmed the bus, in which the OSCE group was travelling, had been stopped and that they were checking the identities of those on-board.
The self-proclaimed mayor of Sloviansk, Vyacheslav Ponomaryov, said that at least one passenger was carrying maps showing separatist checkpoints in the area, which suggested "their involvement in espionage".
Russian Foreign Minister Sergei Lavrov on Friday accused the West of being only interested in the Ukrainian economy and not the welfare of its people.
Lavrov also said that Moscow has been eager to assist in the de-escalation of tension in Ukraine as envisaged by the deal reached during the Russia-US-EU-Ukraine meeting in Geneva on April 17.
He accused Kiev authorities of not implementing the agreement and called on the US to convince Kiev to stop anti-terrorism operations in southeastern Ukraine.
Russia has denied fomenting separatism in eastern and southern Ukraine.(IANS)