U.S. benchmark crude for August delivery gained $1.61, or 1.6 per cent, to close at $99.60 a barrel in New York after rising as high as $99.87. Oil last crossed $100 a barrel on Sept. 14 of last year.
In London, Brent crude rose $1 to finish at $104 a barrel on the ICE Futures exchange.
Protests in Egypt continued as President Mohammed Morsi faced a military ultimatum that gives him until Wednesday to meet the demands of the millions who have taken to the streets seeking his ouster. Traders were concerned that the situation in Egypt, as well as and the civil war in Syria, could affect the production and transport of oil supplies in the Middle East and North Africa.
Traders are also awaiting the U.S. Energy Department's weekly report on U.S. stockpiles of crude oil on Wednesday. Data for the week ending June 28 is expected to show a draw of three million barrels in crude oil stocks, according to a survey of analysts by Platts, the energy information arm of McGraw-Hill Cos.
That would be the first decline in four weeks, and the forecast supported oil prices.
In addition, BP PLC says a new 250,000 barrel-a-day distillation unit at its refinery in Whiting, Indiana, is operational. The unit will initially process light, sweet crude, which analysts expect will mean increased demand for West Texas Intermediate crude, the U.S. benchmark.
In other energy futures trading on the New York Mercantile Exchange:
— Natural gas gained eight cents to end at $3.65 per 1,000 cubic feet.
— Heating oil added three cents to finish at $2.90 per gallon.
— Wholesale gasoline rose five cents to end at $2.78 per gallon.
Pablo Gorondi in Budapest contributed to this report.
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