Manila, Philippines ? Nearly 6,000 U.S. and Philippine troops began joint exercises Monday focusing on war games and construction projects as the countries bolster their relationship amid terrorist threats.

The exercises began after a series of bombs detonated in the city of General Santos during the weekend, killing 14 people and injuring 69. Police blamed Muslim extremists, and President Gloria Macapagal Arroyo on Monday ordered a crackdown on terrorists.

An angry protester hits a mask representing Philippines President Gloria Macapagal Arroyo as others shout anti-U.S. slogans during a rally in front of the American Embassy in Manila. Some 5,600 U.S. and Filipino troops began a three-week joint exercise Monday that will focus on war games and civil projects.

Lt. Cmdr. Jeff Gordon, a U.S. spokesman in Basilan said the projects primarily had military purposes but also will benefit the province. The Philippine government has made development in the Muslim-dominated south a top priority, saying the area’s wrenching poverty breeds extremists like the Abu Sayyaf.

The Abu Sayyaf still hold Wichita, Kan., missionaries Martin and Gracia Burnham and Philippine nurse Ediborah Yap as hostages.

A total of 2,700 American troops and 2,900 Philippine troops launched the three-week joint exercises on the island of Luzon in the northern Philippines. That is hundreds of miles from the southern islands where other U.S. troops are training Philippine forces in a separate operation aimed at wiping out Muslim guerrillas.

The joint exercises are meant to help Washington’s biggest Southeast Asian ally improve its defenses and ability to participate in U.S. peacekeeping activities. They are expected to end May 6, with the last week devoted to civil efforts ranging from construction projects to establishing medical and dental clinics for local residents.

The projects carry risks because communist rebels have warned they will attack any Americans venturing into what the guerrillas claim is their territory.

Two small groups protested Monday outside the U.S. Embassy in Manila, calling the maneuvers which bring temporary U.S. troop strength in this former American territory to about 4,000 an infringement on Philippine sovereignty.

But turnout was much smaller than during protests when U.S. troops arrived in January for a six-month counterterrorism exercise in the south aimed at helping local troops wipe out the Abu Sayyaf.

The Muslim extremist group is believed to have ties to Osama bin Laden’s al-Qaida network and Washington calls the effort an expansion of the global war on terrorism.

That exercise has been more controversial because of the possibility that Americans could end up in combat while serving as advisers to front-line Philippine units. Those 160 U.S. special forces cannot initiate combat, but can shoot back if fired upon.

In the southern Philippine island-province of Basilan, U.S. Marine engineers and Navy Seabees began deploying Monday for construction projects to enhance the counterterrorism campaign.