DAVAO (Philippines), March 4: Twenty people, including an American, were killed and 146 others injured on Tuesday in a powerful bomb attack at the busiest airport in the rebellion-torn southern Philippines, officials said.

The powerful bomb pulverized an unguarded shed outside the Davao airport on the island of Mindanao, where Muslim groups are seeking an independent state and a small number of US military advisers are giving counter-terrorism training to Filipino troops.

It was the deadliest terrorist attack in Southeast Asia since the Oct 12 Bali bomb blast that killed more than 200 people and condemned by US President George Bush and Philippine leader President Gloria Arroyo.

The blast came amid increased guerilla activity in Mindanao before a planned deployment of US troops in the southern stronghold of the Abu Sayyaf group.

“The United States will work shoulder to shoulder with the Philippine government to make certain that those responsible are brought to justice,” a White House spokesman said.

A US embassy spokesman in Manila said one among four Americans injured in the blast succumbed to injuries. He did not identify the victims.

But there were no US military personnel in the injured or death list, Manila-based US military adviser Captain Dennis Williams said.

Davao City mayor Rodrigo Duterte said the blast killed 20 people and injured 146 others, including the Americans.

The death toll made it the worst attack in the Philippines since 1996, when guerillas sacked the Mindanao town of Ipil and killed more than 50 people.

Twenty-two people were also killed in a series of bombings in Manila in Dec 2000.

President Arroyo said police had arrested and were interrogating several men over the Davao blast.

The bombing “is a brazen act of terrorism that will not go unpunished”, she said in a statement that did not name any suspects. “I assure you justice will be done.”

In another blast outside a government clinic in the nearby city of Tagum just after the airport attack, three people were wounded, officials said.

A Davao bus terminal also received a telephoned threat but bomb squads found no explosives there.

The authorities shut down Davao airport as a precaution, while other airports in Mindanao stepped up security.

Mainly Christian Davao has 1.2 million people and is the largest city of the southern Philippines.

“I heard a tremendous explosion, then I saw people sprawling on the ground,” said Bobby Cabanban, who was parking his taxi about five meters away.

“It’s a very powerful bomb. The waiting shed literally exploded,” Davao Vice Mayor Luis Bongoyan said of the late afternoon airport blast.

“We have suspects and we are running after them,” Mindanao’s police chief said. He told a television network the bombers had used the chemical trinitrotoluene (TNT) and had concealed the device in a rucksack.

An hour after the airport blast, ambulances and other emergency vehicles were still picking up casualties from the street outside the airport, cordoned off by yellow police tape and dozens of soldiers armed with assault rifles. —AFP