Philippine police said Wednesday they had seized a Chinese fishing vessel and detained its 11 crew members in South China Sea waters claimed by both countries, in the latest escalation of their bitter maritime row.

National police spokesman Reuben Sindac said the 15-ton Chinese boat had been intercepted Tuesday while fishing off Half Moon Shoal, west of the major Philippine island of Palawan, in what he said were Philippine waters.

Philippine police firing assault rifles stormed a provincial prison Wednesday to pacify rioting inmates, killing four, the authorities said.

Police were called in to quell a "disturbance" involving about 100 inmates of the jail in Lucena city, said regional police spokesman Chief Superintendent Serafin Barreto.

Twenty-three people were injured when fire and a series of explosions struck a Philippine army munitions depot near the country's financial district Wednesday, officials and witnesses said.

Local television footage showed uniformed soldiers carrying some of the injured on stretchers away from a burning building enveloped in black smoke, while three other victims sat on the pavement awaiting medical help.

A Chinese national has been seized in Malaysia's Borneo island by Filipino gunmen, a security official said Tuesday in the wake of tension between Kuala Lumpur and Beijing over missing Malaysia Airlines flight MH370.

Mohammad Mentek, director-general of security in the east of Malaysia's Sabah state, identified the victim as 34-year-old Yang Zai Lin, who worked as a manager at a fish farm.

Communist insurgents who seized 39 gold prospectors in the southern Philippines have released all but three of them, authorities said Monday.

Guerrillas of the New People's Army (NPA) released 36 of the small-scale miners they had abducted on Saturday as government troops closed in on them, said Arturo Uy, the area's governor.

Thousands of American and Philippine troops launched large annual exercises on Monday after U.S. President Barack Obama vowed "ironclad" backing for its Asian ally, locked in a tense maritime row with China.

Filipino Foreign Secretary Albert del Rosario said the 10-day drills were necessary to deal with the challenge of "aggressive" neighbors intent on "changing the status quo".

Fifty-eight people have been arrested in the Philippines for their involvement in a giant, global Internet "sextortion" network, local police and Interpol announced in a joint press conference on Friday.

Victims in foreign countries have been lured by people in the Philippines into giving sexually explicit photos or videos about themselves online, then blackmailed for many thousands of dollars, the authorities said.

The family of a senior Italian diplomat detained in the Philippines for alleged child abuse insisted Wednesday he was innocent, as they accused authorities of misinterpreting his efforts to help homeless children.

Daniele Bosio, 46, was arrested on April 5 following a complaint by members of a children's advocacy group who claimed they saw him acting "inappropriately" with three homeless boys at a water fun park in Manila.

President Barack Obama landed in the Philippines Monday to cement new defense ties on the last leg of an Asian tour conducted against a backdrop of territorial tensions between U.S. allies and China.

Obama flew into Manila from Malaysia, hours after the allies signed a new defense agreement allowing more U.S. troops and defense hardware to rotate through the Philippines, part of a U.S. re balancing of military power towards rising Asia. 

The Philippines said it would sign an agreement on Monday with the United States to allow a greater U.S. military presence on its territory, giving it a security boost amid a bitter territorial dispute with China.

A statement from the Department of National Defense on Sunday said the signing would take place in Manila on Monday morning, a few hours before U.S. President Barack Obama is due to arrive for a two-day visit.