Eight people were killed in the southern Philippines when a rusty mortar round they thought was an iron canister with gold inside exploded as they tried to pry it open with a hammer, police said Thursday.

Police Senior Superintendent Raul Tacaca said by telephone that five other people were wounded by the powerful blast late Wednesday in a far-flung mountain village of Sirawai town in Zamboanga del Norte province. The explosion happened inside a bunkhouse for workers of a plywood company.

One of the workers found the mortar round in a river bank and brought it to the bunkhouse, where other workers and their relatives stayed, and started to try to open it with a hammer, Tacaca said.

"They pounded on it, thinking there may be gold inside," Tacaca said.

Six of the victims died in the bunkhouse, which was destroyed by the blast, and two others died while being brought to a hospital, he said.

Some villagers believed the mortar round may have been a relic of World War II, but Tacaca said it appeared to have been a leftover of clashes between government forces and Muslim rebels in more recent years.

Zamboanga del Norte is one of several coastal areas that were battered by a tropical storm last month that left more than 160 people dead and scores other missing in flash floods and landslides.