Amid signs of deterioration in the global macroeconomy, investors are reducing their long position in crude oil and this caused the Brent crude oil futures to decline below $100 a barrel.
This is for the first time in nine months that the Brent crude oil futures slipped below $100-mark.
Analysts expect that the slowdown in economic growth in the world's fastest growing economy China may reduce demand for crude oil.
Brent crude for June delivery dropped $2.31 to $98.32 per barrel in recent trading sessions, the lowest since July 2012.
The NYMEX crude for May delivery declined $2.17 to $86.54 a barrel in recent sessions, the weakest since December 2012.
The slower than expected growth in the GDP of China, which is the second largest oil consumer, during Jan-Mar 2013, prompted analysts to expect moderate demand for crude oil.
The International Energy Agency, the US Energy Information Administration and the Organization of the Petroleum Exporting Countries have all forecast lower global oil demand growth for 2013.