Brent North Sea crude for delivery in March gained 75 cents to $100.58 per barrel in late morning London trade.
New York's main futures contract, light sweet crude for March, won 33 cents to $89.36 a barrel.
Prices soared beyond the key $100 mark in London last week for the first time in more than two years -- and went on to cross $103 as sentiment was hit by concerns over the impact of Egypt unrest on global energy supplies.
But the market ran out of steam on Friday as traders took profits amid weak jobless data in the United States, which is the world's biggest crude consuming nation.
"The price of Brent has climbed above the $100 mark again this morning, after dipping below this mark in Friday's late trading and closing below it due to profit-taking before the weekend after weaker-than-expected US labour market data," said Commerzbank commodities analyst Carsten Fritsch.
"On the back of continued protests in the Middle East, oil prices remain well protected on the downside," added Fritsch.
"The unrest in Egypt has also had an impact on the behaviour of speculative financial investors, who are increasingly betting on rising oil prices again amid the uncertainty about possible effects on oil supply."
Egyptian President Hosni Mubarak came under fresh pressure on Monday to step down as opponents said concessions made in landmark talks were not enough to halt a revolt against his 30-year rule.
Thousands of demonstrators spent Sunday night under blankets and tarpaulins in central Cairo's Tahrir Square, or Liberation Square, which over two weeks has begun to resemble a tented camp.

While Egypt is not a major crude producer, the country is home to the Suez Canal, which carries about 2.4 million barrels daily, roughly equal to Iraq's output.
On the back of Egypt concerns, Brent had crude spiked as high as $103.37 last Thursday -- reaching the highest level since September 26, 2008.
The price of New York crude lags behind Brent owing to large supplies of oil remaining at the US port of Cushing, Oklahoma, according to analysts.