LAHORE, Pakistan (AP) _ A bomb exploded today in the terminal of Lahore's international airport, killing nine people, wounding 20 and heavily damaging the main departure lounge.

The bomb was slipped through airport security inside a briefcase, and exploded near a telephone booth by the main departure lounge, investigators told the official Pakistani news agency.

It blew up as Pakistan International Airlines Flight 315 was leaving for the southern port city of Karachi, and police told the agency it may have been intended for that plane.

Today's bomb was the 13th this year in Punjab province, most targeting buses and public buildings. Prime Minister Benazir Bhutto has accused India of orchestrating the bombings in a bid to destabilize Pakistan's most populous province. India denies it.

Police would not say who was suspected in today's bombing.

The briefcase bomb, tucked under a concrete bench, was either a time bomb or was triggered by remote control, said Wasi Zafar, special assistant to the Punjab provincial Home Ministry.

Three of the nine people killed died at a hospital in central Lahore. Doctors said some of the wounds appeared to be from shrapnel.

The airport's main departure lounge, crowded with small shops and kiosks, typically is full of travelers and their relatives.

Walls were blackened and luggage was strewn amid debris from the blast, witnesses said. At least four airline ticket booths were heavily damaged. A column of black smoke could be seen rising from the airport.

``There was a very big bang and then the smoke,'' said Fazal Abdullah, who was arriving at the airport at the time of the blast. ``I didn't know what was going on.''

Federal investigators closed the airport.

Two large explosions in Punjab province in late April and early May killed 52 people and injured dozens more. Another bomb in April exploded in former cricket star Imran Khan's charity cancer hospital in Lahore, the provincial capital, killing six people.

Last month, three separate bomb explosions rocked the central city of Gujranwala, killing at least eight people. The largest of the bombs tore through a commuter bus arriving from Lahore.

Pakistan and India each accuse the other of acts of terrorism, and each denies them.

Pakistan was formed from Islamic majority areas of India and gained self-government after British withdrew from the area in 1947.

Pakistan became a republic nine years later. Since then, the two countries have fought three wars.