(Updates with five injured, adds byline)

By Ranga Sirilal

COLOMBO, Sept 29 (Reuters) - A bomb hidden inside a van exploded in a market area of of Sri Lanka's capital Colombo on Monday, wounding five people and damaging nearby vehicles, authorities said.

Police said the bomb was the latest set off by the Liberation Tigers of Tamil Eelam (LTTE), separatist guerrillas who are fighting one of the world's longest-running insurgencies since taking up arms against the government in 1983. "The bomb was placed under a van, in the floor," the police spokesman, Senior Superintendent of Police Ranjith Gunasekara, said. "This must be LTTE."

The blast took place in Pettah, a market area which is adjacent to Fort, a heavily guarded zone full of government offices where police initially said the explosion was heard.

Five people were admitted to Colombo National Hospital with minor injuries, hospital director Dr. Hector Weerasinghe said.

This is the sixth blast in the capital of the Indian Ocean island nation since Aug. 30, when an explosion in Pettah wounded 45 people. That was the worst attack in the period.

Police say all but one of those bombs were the work of the Tamil Tigers, against whom the military has stepped up an offensive this year in the north of the island with the goal of eradicating them and ending the war.

The rebels, who never claim responsibility for blasts, could not be reached for comment. The Tigers are on terror lists in the United States, European Union and India, and are credited with perfecting the suicide bomb as a weapon.

They are seeking a separate homeland for Sri Lanka's minority Tamil people.

The army has said it believes the Tigers will carry out more guerrilla attacks now that their conventional fighting capacity is being cut down by the northern offensive. (Writing by Bryson Hull; Editing by Valerie Lee)

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