Colombo, Sri Lanka ? Sri Lankan forces captured the Tamil Tigers’ de facto capital Friday, winning a major victory in a decades-long battle to destroy the ethnic separatists and crush their dream of establishing an independent state.

The rebels, who still control 620 square miles of northeastern jungle — an area about the size of Los Angeles — swiftly sent the message they would fight on. They carried out a suicide attack near air force headquarters in the capital, Colombo, killing three airmen and wounding 37 other people, authorities said.

Sri Lanka’s ethnic minority Tamils have long complained they are treated as second-class citizens, with Sinhalese used as the nation’s de facto official language and members of the dominant group traditionally favored for government jobs. They have also accused the government of sending Sinhalese settlers into traditionally Tamil regions to overwhelm them demographically.

The fall of Kilinochchi was a devastating blow to the rebels’ dream of establishing a state for Tamils in the northeast after decades of marginalization by governments controlled by the Sinhalese majority.

The rebels had built a massive 10.5 mile-long earth and moat fortification to defend Kilinochchi. Over the past two months, they held off government troops — with the aid of pounding monsoon rains, in battles that reportedly killed hundreds of fighters.

But Army troops cleared the way into the town Thursday when they captured a key crossroad north of Kilinochchi that allowed them to close in from three directions, the military said.

They said they entered Kilinochchi the following morning with only minimal resistance, an apparent sign the rebels had retreated to their northeastern jungle bases to fight another day, analysts said. The rebel-affiliated TamilNet Web site said the Tamil Tigers had moved their headquarters farther to the northeast before the town fell.

The capture of Kilinochchi was a milestone in a civil war that has killed at least 70,000 people and plagued this Indian Ocean island nation off and on for 25 years. A 2002 cease-fire collapsed in new fighting three years ago, and government forces have pushed deep into the rebels’ heartland in the jungles of the north in recent months.

Foreign mediators have called for a political solution to the fighting, saying that warfare will not resolve the underlying tensions between the Tamil minority, which makes up 18 percent of the population, and the Sinhalese majority that accounts for 74 percent of the country.

The Tamil Tigers have been blamed for scores of bombings and suicide attacks and are listed as a terror group by the United States and European Union.

In Washington, State Department spokesman Gordon Duguid described the Tigers as “one of the most notorious and brutal terrorist organizations” but called for a peaceful dialogue to resolve the legitimate concerns of Tamils.

President Mahinda Rajapaksa, who has vowed to destroy the group formally known as the Liberation Tigers of Tamil Eelam, announced the fall of Kilinochchi in a nationally televised speech.

“Our brave and heroic troops have fully captured Kilinochchi, which was considered the main bastion of the LTTE,” he said, as Cabinet ministers erupted in applause. “For the last time, I call upon the LTTE to lay down their arms and surrender.”

Officials with the Tamil Tigers could not be reached for comment.

Celebrations erupted across Colombo, where people flooded the streets, dancing, waving Sri Lankan flags and setting off firecrackers.

But less than an hour after Rajapaksa’s speech, a suspected rebel suicide attacker blew himself up near air force headquarters in the heart of Colombo among troops heading home in the busy afternoon rush hour, air force spokesman Wing Commander Janaka Nanayakkara said. Among the 37 injured were 16 airmen, he said.