Three mosques in the south Philippines city of Davao have been hit by a series of attacks, just hours after a deadly bombing killed 16 people.
Davao, once a peaceful city, is reeling from the violence
The mosque attacks prompted fears of a spiral of religious violence in the mainly Christian city.
Military vice-chief of staff Lieutenant General Rodolfo Garcia said the mosque attacks might be "a retaliatory action" for the bombing, but added that this should not be allowed to become a "religious confrontation".
The initial bombing, at the city's bustling Sasa wharf at dusk on Wednesday, killed 16 people and injured at least 40. The bomb was hidden in a barbecue stand and tore through the crowds leaving a ferry terminal.
A nun and at least one child were among the dead.
The bomb was followed by attacks in Muslim or mixed districts of the city.
At about 0200 on Thursday local time (1800 GMT on Wednesday), five hooded men in a car hurled two grenades and directed rifle fire at a mosque in the southern, mainly Muslim district of Tibungco before fleeing
Minutes later, a bomb exploded outside a mosque in the mixed Christian-Muslim district of Toril
A blast at a ferry terminal killed 16 people
Less than an hour later, unidentified men in black jackets hurled a home-made bomb near a mosque in the mainly Muslim
district on Roxas Boulevard, shattering the mosque's windows
There were no reports of casualties.
No group has claimed responsibility for any of the attacks, and police would not comment on any link between them.
Davao is on the island of Mindanao, the heartland of the Philippines' small Muslim minority, where rebels have been waging a bitter war for a separate homeland.
President Gloria Arroyo, who visited Davao to offer her sympathy and inspect the damage from Wednesday's bomb, declared a "total war" on terrorism.
Police have a sketch of a 36-year-old male suspect based on witness statements, spokesman Senior Superintendent Eric Javier told the Associated Press.
President Arroyo issued an order late on Wednesday for the military and police to take "all appropriate measures" against "lawless elements and terrorists".
Davao had largely escaped the three decades of violence in the southern Philippines, until a huge bomb blast at the city's airport last month, in which 23 people died and more than 150 others were injured.
That attack was blamed by police on the main Muslim rebel group in the region, the Moro Islamic Liberation Front (MILF). The MILF said it was not responsible.
The MILF also denied any part in the latest violence.
The group has been engaged in fresh fighting with the government in recent months. But on Sunday, it agreed to hold peace talks with Mrs Arroyo's administration following an initial two-day meeting between both sides in Malaysia.