Manila  - Air force helicopters joined Tuesday in the search for at least 28 people missing after an overloaded boat capsized and sank in the northern Philippines, killing at least 27 people.

Lieutenant Commander Ferdinand Panganiban, a local coast guard commander, said 45 people survived the sinking Sunday of the MB Maejan off the coast of Ballesteros town in Cagayan province, 420 kilometres north of Manila.

Panganiban said rescuers were scouring nearby islands and islets in hopes of recovering more survivors who might have been able to swim to safety.

Maejan left Calayan Island for the mainland town of Aparri when it was battered by huge waves and strong winds, causing it to capsize.

Rescuers were suspecting that more people might have been trapped inside the ill-fated vessel, which was only allowed to carry 40 passengers and 10 crew members.

"The number of people aboard the vessel reach at least 100, but it was only authorized to carry 50," Panganiban said.

Sea travel is a major mode of transportation in the Philippines, an archipelago of more than 7,000 islands.

In June, more than 800 people were killed when a passenger ferry sank in storm-whipped seas off the island province of Romblon in the central Philippines. Fifty-six people survived that accident.

The country was the site of the world's worst peacetime shipping disaster in 1987 when more than 4,000 people perished in a collision between a Philippine passenger ferry and a foreign oil tanker just before Christmas. (dpa)