Seven people are missing and four others were rescued at sea after two small passenger boats capsized in bad weather off the western Philippine island of Palawan, police said Friday.

The boats were ferrying local residents of tiny islands around the municipality of Araceli in the Sulu Sea when they separately ran into strong winds in the same area on Wednesday, the Araceli police chief told AFP.

The four people on board one of the outrigger boats were rescued unharmed on Thursday, while those on the second vessel remain missing, police Captain Orland Sagaro said.

"There was no storm but the northeast monsoons are quite strong in these parts. They likely took in water before they flipped over," he added.

The navy, coast guard and rescuers from the municipal government are all taking part in the search for the second vessel and its seven passengers and crew, Sagaro said.

Sea accidents are frequent in the Philippines, a storm-struck Asian archipelago of more than 7,000 islands with poorly regulated domestic shipping.