. The security media centre of the defence ministry said the explosion occurred at 2.05 pm.
Earlier on Sunday a hand grenade exploded in a zoo in the suburb of Dehiwala, but no one was killed.
The bombings came as the country was getting ready to celebrate 60 years of independence from British colonial rule on February 04 and the capital was under a tight security blanket.
Police have blamed the Tamil Tigers for earlier bombings which have targeted civilians.
In January Sri Lanka pulled out of a ceasefire with the Tamil Tigers, who have been fighting for a separate state in the island for nearly three decades.