The United States said it has suspended defence cooperation with Russia and the UN Security Council began a meeting on the crisis.

US benchmark West Texas Intermediate (WTI) for April delivery, eased 13 cents to $104.79 in mid-morning trade on profit-taking as after hitting its highest levels this year in New York on Monday.

Brent North Sea crude for April climbed two cents to $111.22.

Producing more than 10 million barrels a day in January, Russia vies with Saudi Arabia as the world's largest crude oil producer, and is the second-largest producer of natural gas.

More than 70 percent of its gas and oil exports to Europe pass through Ukraine.

"The Ukraine event is a new catalyst that propped up crude oil prices to form new highs," Phillip Futures said in a market commentary.

"When war erupts, Russia, one of the world's top oil producers, is likely to reduce oil exports due to higher domestic consumption."

It warned that any possible disruption to oil infrastructure could hit production, leading to tighter supplies.

Research house Capital Economics noted that "Europe is heavily dependent on supplies of Russian energy".

Ukraine on Monday accused Russia of pouring more troops into Crimea as world leaders grappled with Europe's worst crisis since the Cold War and global stock markets tumbled on fears of an all-out conflict.

Crimea has been under de facto occupation by Moscow-backed forces since President Vladimir Putin won parliament's authorisation on Saturday to send troops into Ukraine.