June 6 (Bloomberg) -- A bomb targeted a bus near the Sri Lankan capital, Colombo, today, killing 21 civilians and injuring more than 50 others, the Defense Ministry said.

The military blamed the attack on the Liberation Tigers of Tamil Eelam, saying the rebels used a ``claymore bomb targeting a crowded public transport bus'' near a Buddhist temple in Moratuwa, about 21 kilometers (13 miles) south of Colombo. The attack is the deadliest since at least 24 people were killed in a bus bombing near the capital on April 25.

It is the second bombing near Colombo since May 26 when at least nine people were killed on a train, an incident the government also blamed on the LTTE. Eighteen passengers were injured when a bomb exploded near a train two days ago and police said they arrested an LTTE member who admitted his role in that attack.

The Tamil Tigers have been fighting for 25 years for a separate Tamil homeland in the island's east and north. The group's military spokesman Irasiah Ilanthirayan was unavailable for comment when contacted by telephone at its headquarters in the northern town of Kilinochchi.

LTTE political chief B. Nadesan, in an interview with TamilNet published May 30, said the rebels aren't targeting civilians in the south.

Peace Settlement

Tamils make up 11.9 percent of Sri Lanka's population and Sinhalese almost 74 percent, according to a 2001 census. The government says it won't consider any peace settlement with the LTTE that divides the country of 20 million people.

Sri Lanka's military is staging almost daily attacks on the LTTE's estimated 7,000 fighters in the north, the last region held by the group after it lost control of Eastern Province 11 months ago.

President Mahinda Rajapaksa's government has vowed to eradicate terrorism on the island while seeking a settlement with all Tamil groups. It ended a 2002 cease-fire with the LTTE in January, prompting the United Nations to call on the government and the Tamil Tigers to prevent an escalation of violence against civilians.

The LTTE, designated a terrorist organization by the U.S., the European Union and India, said in March the military offensives in the north amount to genocide and accused the air force of dropping bombs in civilian areas.

The group said last month that 17 civilians from the same family were killed when a landmine placed by the military exploded near their vehicle in the north. The armed forces denied any involvement in the deaths.

``This is a regular pattern of both parties allegedly targeting civilians. There is an element of tit-for-tat,'' Jehan Perera, director of the National Peace Council, a Sri Lankan non-governmental advocacy organization, said by telephone today from Colombo. ``It also represents how in an escalating internal war, anyone can become a target. It is part of a larger psychological warfare.''

Such attacks ``harden feelings,'' he said. ``So there is no chance that the two parties will return to the negotiating table.''

To contact the reporter on this story: Ed Johnson in Sydney at ejohnson28@bloomberg.net.

Last Updated: June 6, 2008 01:13 EDT