CAGAYAN DE ORO, Philippines -- A homemade bomb ripped through a row of upscale bars and restaurants in a southern Philippine city, killing six people and wounding at least 46 others, police said Saturday.

The victims of the blast late Friday were mostly medical representatives and guests of a pharmaceutical company who were attending a medical conference in one of the restaurants, said Cagayan de Oro police chief Graciano Mijares.

Among the fatalities was a provincial legislator, Roldan Lagbas, 44, who was at an open air bar when hit by shrapnel in the head, Mijares said.

Teddy Sabuga-a, the city government's acting social welfare officer, said seven of the wounded were in serious condition, with most of the injured suffering only minor cuts.

Bomb fragments were recovered as far as 50 metres (yards) away from a table thought to have been where the device was placed, Mijares said.

He said an investigation was under way to determine the motive for the attack and to identify suspects.

Supt. Marino Pongtilan, chief of the regional police explosives unit, said the bomb was made from a mortar shell and was triggered with a cellphone circuit board.

City Mayor Oscar Moreno told ABS-CBN television that military and justice department agents were assisting in the investigation.

Cagayan de Oro, about 800 kilometres (500 miles) south of Manila, is a relatively peaceful port city in the southern Mindanao region where al-Qaida-linked militants, communist rebels and heavily armed crime gangs operate.