New York's benchmark, West Texas Intermediate for delivery in June, climbed 34 cents to USD 99.76 a barrel.
In London, Brent North Sea crude for June added 83 cents to close at USD 108.59 a barrel. Moscow's warning to Kiev over its attack on pro-Russia secessionists in Ukraine's east raised more worries over a Russian intervention, which could further strain relations with the West.
Ukraine today launched a military assault on the flashpoint town of Slavyansk, but insurgents shot down two army helicopters, killing two servicemen, including a pilot. The crisis also spread to the southern city of Odessa, where 38 people died in an arson attack against a trade union building after a day of violent clashes between pro-Russian and pro-Ukrainian militants. "The escalating conflict in east Ukraine is allowing oil prices to recover after finding themselves under pressure," said Commerzbank analyst Carsten Fritsch.
Ukraine, a major conduit for Russian natural gas exports to Western Europe, is monitored closely by investors who are concerned that a full-scale armed conflict will disrupt supplies and send energy prices soaring.
A robust US job report for April, with the jobless rate sharply falling to 6.3 per cent, signaled a stronger economy, also helping to boost crude prices. "Some support to the market is coming from the better- than-expected job report this morning, showing a significant number of jobs that will translate into demand for petroleum products," said Andy Lipow of Lipow Oil Associates.