The Philippine president yesterday promised swift justice for the bombing of Davao's bustling wharf that killed 16 people, and warned that relentless, rising terrorism can be contained only with "collective vigilance."

　　Nosgroupshas claimed responsibility for Wednesday's blast, the second deadly attack in the southern Philippine city in less than a month.

　　On a visit yesterday to Davao, Arroyo assured the nation "justice will be done" and promised a speedy, thorough investigation.

　　The separatist Moro Islamic Liberation Front, blamed for a similar March 4 bombing at Davao's airport that killed 21 people, denied involvement. Authorities, who in the past have been quick to blame the guerrillas, avoided jumping to any conclusion with no suspects in custody.

　　Underlining the tensions in this predominantly Roman Catholic city with a sizable Muslim minority, unidentified gunmen lobbed two grenades and used a machine gun to strafe a Davao mosque, police said. There were no casualties.

　　Wednesday's bombing was carried out by a man who posed as a ferry passenger and mingled with the crowd before leaving a plastic bag that exploded at a barbecue stall outside the fenced-in ferry terminal, police chief Supt. Isidro Lapena said. He said traces of potassium nitrate were found.

　　Forty people were injured in the blast, and two children and a nun were among those killed. Many victims were customers and operators of food stalls that lined the street near the fence perimeter.

　　"We have a sketch of the suspect based on description of witnesses," said police spokesman Senior Supt. Eric Javier. Javier described him as a male about 36 years old.

　　Police said they were questioning several people, but none was considered a suspect.

　　Davao Mayor Rodrigo Duterte said all leads and theories were being explored. He refused to link the March bombing to Wednesday's blast.

　　The string of attacks in the volatile south came during a debate over the mandate of US troops in the war on terror in the Philippines,swheresMuslim insurgents have battled the government for decades.