U.S. President Barack Obama will travel to Japan, South Korea, Malaysia and the Philippines in April, the White House said Wednesday.

The visit is intended to quell doubts in the region about Obama's strategy of rebalancing U.S. power to Asia, following the cancellation of his last planned trip there in October for domestic political reasons.

The Philippine military said Monday it had killed six members of an al Qaida-linked group that is holding three foreign hostages in the volatile south of the country.

The military launched an assault on Saturday against dozens of Abu Sayyaf militants hiding in and around a remote village on Jolo island, where the militants are holding two European tourists and a Japanese.

Two foreigners were among 14 people killed when a tourist bus fell into a deep ravine in the mountainous northern Philippines on Friday, authorities said.

The bus plunged about 120 meters (nearly 400 feet) while travelling on a narrow road heading to an area famous for its "hanging coffins", said a report from the civil defense office.

Philippine President Benigno Aquino has compared China's efforts to claim disputed territories with those of Nazi Germany's, while urging world leaders not to make the same mistake of appeasement, according to the New York Times.

The Philippines has accused China of becoming increasingly aggressive in recent years in staking its claims to nearly all of the South China Sea, and Aquino reportedly said his nation could not stand up to its mightier neighbor alone.

Five people were injured Sunday when motorcycle-riding men hurled a grenade into a church in the troubled southern Philippines in a city known for Muslim rebel activity, officials said.

One of two men on the motorcycle threw the grenade into the Roman Catholic church in a suburb of the city of Zamboanga just as a group of senior citizens were meeting there, police and district officials said.

A homemade bomb that was likely set off by Muslim rebels in the southern Philippines wounded six people, including two television journalists, the military said.

The blast happened near an area where government troops have been battling Muslim insurgents that broke away from a larger rebel group, the Moro Islamic Liberation Front, which recently signed a peace deal with the government.

Three child soldiers recruited by hardline Muslim rebels were among 53 people killed in a week of fighting with the Philippine army, a military official said on Friday.

Regional spokesman Colonel Dickson Hermoso said the offensive against members of the Bangsamoro Islamic Freedom Fighters (BIFF) group in the strife-torn southern island of Mindanao had resulted in the deaths of 52 rebels, including the children, and one soldier.

The Philippines' chief peace negotiator with Muslim rebels called Thursday on breakaway guerrillas still fighting the government to turn themselves in, as the death toll from this week's clashes rose to 41.

Negotiator Miriam Coronel said the main Muslim rebel group, the Moro Islamic Liberation Front (MILF), was working with government forces to contain the breakaway group and stop the fighting spreading from remote villages in the southern island of Mindanao.

The Philippines insisted Thursday it would not apologize for a 2010 hostage crisis in which Hong Kong tourists died, saying its response to the tragedy had been generous and compassionate.

The statement came after the Hong Kong government announced on Wednesday it would impose diplomatic sanctions against the Philippines because of its "unacceptable" failure to apologize.

Philippine President Benigno Aquino vowed Wednesday to crush militants opposed to an imminent deal aimed at ending a decades-long Muslim separatist insurgency, as the death toll from a military assault on them rose to 38.

The government wrapped up peace talks with the nation's biggest Muslim rebel group on Saturday, then quickly deployed the military against a hardline splinter faction called the Bangsamoro Islamic Freedom Fighters (BIFF).