At least 18 people were killed and over 37 injured when a powerful bomb exploded in a busy market area near the Sri Lankan capital on Wednesday, hours after a suspected woman Tamil Tigers suicide bomber blew herself up in the office of a minister and senior Tamil political leader which left one of his aides dead.

The explosion in Nugegoda, 10 kms from here, took place when a suspected Liberation Tigers of Tamil Eelam militant handed over a parcel bomb to the bag counter of the popular NOLIMIT garment store, police said.

A man handed over a parcel to the bag counter of the store before entering, and a few minutes later, walked out without collecting it from the counter, sources said quoting shop assistants. The parcel exploded after some time.

The powerful blast led to a minor fire, which spread to several adjoining buildings. "The nature of the target indicates that the attack was deliberately perpetrated against innocent civilians," a government statement said.

The blast came hours after Social Services and Social Welfare Minister Douglas Devananda, a senior Tamil political leader, escaped unhurt when a suspected LTTE suicide bomber blew herself up in his office.

The bomber, a physically challenged woman, got past one layer of security in the office of Devananda but detonated the bomb when she was stopped at the second check-post near his room, officials said.

The Public Relations Officer of the Minister, Stephen Perras, was wounded and died in a hospital, they said, adding one of Devananda's bodyguards was seriously injured.