U.S. crude oil price plunged on Friday and settled below 100 dollars a barrel for the first time since Feb. 13 on rising concerns over global economy.

The Labor Department said U.S. nonfarm payrolls added 115,000 in April, less than expectation of 170,000. The unemployment rate fell to 8.1 percent from 8.2 percent a month earlier.

The job report was "not terrible", but also "not good", said Raymond Carbone, president of energy brokerage Paramount Options. Two straight months of disappointing job data heavily weighed on the crude markets. Carbone said that oil has fallen since Wednesday as a string of weak data worsened the worries about a slow-down in U.S. economic recovery.

Meanwhile, investors were concerned about euro zone's economic and political outlook. Several euro zone countries declared to have fallen into double-dip recession and the bloc's unemployment rate hit 15-year high. Besides, president elections in Greece and France made the markets nervous. Carbone said that French president challenger Francois Horlande would bring political uncertainties to Europe's economic future as he had different opinion from Germany's Chancellor Angela Merkel in some crucial areas.

On the supplies side, OPEC was pumping the most oil in two years. And military strikes against Iran were temporarily impossible, which could be translated into sufficient oil outflows from the second OPEC oil exporter.

Light, sweet crude for June delivery tumbled 4.05 dollars, or 3. 95 percent to settle at 98.49 dollars a barrel on the New York Mercantile Exchange, posting the biggest one-day drop this year. For this week, WTI slipped 6.44 dollars, or 6.14 percent.

In London, Brent crude for June delivery also declined sharply and last traded around 112 dollars a barrel.