Benchmark West Texas Intermediate crude for February delivery rose 77 cents to close at $100.32 in trading on the New York Mercantile Exchange.
The price got a boost from a drop in applications for unemployment benefits and expectations of a decline in U.S. crude stockpiles.
Both inspired optimism about the U.S. economic recovery and, in turn, lifted expectations for energy demand.
The last time oil traded above $100 a barrel was Oct. 21. The last day it closed above $100 a barrel was Oct. 18. During the abridged holiday trading week, oil gained $1.
A report from the Energy Department's Energy Information Administration released Friday showed that U.S. crude stockpiles fell 4.7 million barrels last week to 367.6 million barrels. The supply fell in the last week from 23.4 days' worth of oil to 22.8 days.
Meanwhile, violence in south Sudan has stoked concerns about the African country's oil production.
"Violence flaring in south Sudan threatens to disrupt crude output in the region and with ongoing outages in Libya, Brent prices may gain further support from a tightening fundamental outlook," said analysts in a note from Sucden Financial Research.
Brent crude, a benchmark for international oils, rose 20 cents to US$112.18 a barrel on the ICE Futures exchange in London.
In other energy futures trading on the Nymex, wholesale gasoline was down 0.4 cents at US$2.82 a U.S. gallon (3.79 litres), heating oil was rose three cents to US$3.12 a gallon and natural gas lost three cents to US$4.41 per 1,000 cubic feet.
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