New York's main contract, light sweet crude for delivery in January, fell 32 cents to $97.35 a barrel.

Brent North Sea crude for January delivery shed 28 cents to $107.28.

"Oil is continuing the trend from last Friday in the US, it's heading down," said Victor Shum, senior principal of Purvin and Gertz energy consultants in Singapore, adding that "there are concerns about the European economies."

Spain's conservative Popular Party swept to victory in Sunday's general election and now has the task of pushing through severe austerity measures in the eurozone's fourth biggest economy.

The Socialists are the latest in a series of scalps claimed by the region's debt crisis, which shows no signs of abating.

Governments in Portugal, Italy, Ireland, Greece and now Spain have been deposed by economic turmoil.