Arroyo planned to go ahead with a scheduled visit to Davao on Thursday. But she said the city was "in a state of lawless violence" and she would order the military to help police crack down on "lawless elements and terrorists." 

With a ship getting ready to leave, the area outside the wharf's gates - where passengers can catch public transport or eat at a row of food stalls - was teeming with people when the bomb exploded at about 7 p.m., blasting a shallow crater along the highway in the city's Sasa district. 

Farewells turned to cries of pain and anguish. Health official Dolores Castillo said many victims were vendors and children. A Roman Catholic nun who just arrived on a boat was killed as she sat in the back of a car stalled in traffic while leaving the wharf. Another nun and the driver were injured, witnesses said. 

Larry Laura, 39, was driving a van about 100 yards from the site when the bomb went off. 

"I ... saw people shocked, speechless, crying and just watching bodies scattered on the ground a few seconds after the blast," he said. 

Police chief Supt. Isidro Lapena said initial investigations indicated the bomb was stashed in a barbecue food stall. 

"We think the security at the pier worked because the attackers were not able to bring the explosive inside," Lapena said. 

Arroyo, who chastised officials at Manila's international airport and largest mall for lax security during surprise visits last week, went on radio to urge vigilance. 

"We must not be intimidated," she said. "The police and the military alone cannot do the job. This is a total war requiring the full attention and resources of the entire community. 

"Each citizen must be the eyes and ears to sense danger and initiative to immediately report to authorities." 

Davao Mayor Rodrigo Duterte asked people to avoid carrying bags, including backpacks, in the city unless they were traveling, saying he ordered police to inspect them for possible bombs. 

"I strongly condemn this cowardly monstrous and dastardly act," Duterte said. "Once again, the same criminals and terrorists are testing our patience and strong resolve to continue with our lives despite what had previously happened to us. But we will not be cowed and will never allow them to succeed." 

No one has been arrested in last month's bombing but warrants have been issued for MILF leaders. 

Rebel spokesman Eid Kabalu condemned Wednesday's attack. 

"This heinous act has no place in the MILF," Kabalu said. "The attacker is a lunatic, a crazed man, killing innocent people. Politically there is nothing to gain from this attack." 

The guerrillas also denied responsibility for the previous bombing, suggesting the military might have staged it to bolster U.S. plans to send 1,000 troops to the southern Philippines to fight another violent Muslim group, the Abu Sayyaf. 

The deployment was put on hold after Philippine officials balked at Pentagon statements suggesting U.S. troops might be allowed to participate in combat against the Abu Sayyaf, which is notorious for kidnappings and killings and has been linked to the al-Qaida terror network. 

A Southern Baptist missionary was killed in the March 4 bombing. Three other Americans - another missionary and her two children - were among the 150 people wounded. 

On Sunday, government negotiators and MILF officials said at Malaysian-brokered talks in Kuala Lumpur that they have agreed to work toward resuming peace talks. Fighting has raged in recent weeks.