New York's main contract, light sweet crude for delivery in April, dipped $2.12 to $99.07 per barrel, while Brent North Sea crude for April lost $2.25 cents to $111.42 in the afternoon.

Analysts said oil demand from Japan which has been hammered by the earthquake and tsunami disaster will likely recover in the longer term as the economy recovers from the devastation.

"Crude oil demand (from Japan) will therefore decrease but then Japan will likely boost import of oil products such as fuel oil and diesel fuel for power generation use," said Victor Shum, senior principal for Purvin and Gertz energy consultancy in Singapore.

Japan, the world's third largest economy, is also the third largest oil-consuming country.

The Asian powerhouse was hit by a massive 9.0-magnitude earthquake on Friday, unleashing a tsunami that battered the country's northeast coast and stretched across the Pacific.

The quake also damaged nuclear power plants, on which the country relies heavily for energy, with concerns growing that one near Tokyo could go into meltdown following several blasts since Saturday.

But continuing unrest in the crude-producing Middle East is also on investors' radar, analysts said.

Saudi Arabia on Monday sent troops into Bahrain to help restore order in the Gulf kingdom amid pro-democracy protests.

The Saudi government said it had responded to a call for help from its neighbour as Saudi-led forces from the Gulf countries' joint Peninsula Shield Force crossed the causeway separating the two countries.