At least seven people have died and dozens have been injured after a trio of bomb attacks in the Philippines.
The Manila blast hit the Makati financial district
A bus is reported to have exploded in central Manila, shortly after two other blasts in the south of the country.
The separatist group Abu Sayyaf, which is currently fighting Philippines troops on the island of Jolo, said it was responsible for the explosions.
A rebel spokesman reportedly told local radio the attacks were a "Valentine's gift" to President Gloria Arroyo.
Presidential spokesman Ignacio Bunye described the bombings as "despicable acts", and warned that the Philippines needed to "brace itself against these attacks on our freedom and security".
One blast happened in General Santos City, when a bomb destroyed a parked motorcycle taxi outside a shopping mall, killing at least three people.
"There was a loud explosion... The ground was shaking. People were screaming and running in all directions," a witness told Reuters news agency.
National police chief Edgar Aglipay said the bomb was believed to have been stashed in a bag at a taxi stand near the entrance to the mall.
Almost simultaneously, a bomb exploded at a bus terminal in Davao City. A 12-year-old boy is reported to have died in the attack.
Davao's mayor Rodrigo Duterte called it "the handiwork of terrorists", and vowed to "track the killers down".
About half an hour later, a third blast went off in the Makati business district of the capital, Manila, killing at least three people.
One witness said smoke could be seen from below a nearby elevated-train station. The bus itself was reduced to a heap of twisted metal, bystanders said.
6:30pm (10:30 GMT): Blast hits Gaisano Mall in General Santos, killing at least three
6:30pm (10:30 GMT): Bomb detonates at bus terminal in Davao, killing at least one
6:50pm ( 10:50 GMT): Abu Sayyaf leader, Abu Solaiman, claims responsibility
7:00pm (11:00 GMT): Bus bursts into flames in central Manila, killing at least three
In a phone call to DZBB radio after the first two attacks, Abu Sayyaf spokesman Abu Solaiman said the militant group was responsible.
"Our latest operations - planned and executed with precision by the gallant warriors of Islam - is our continuing response to the Philippine government's atrocities committed against Muslims everywhere," Mr Solaiman said.
"We will find more ways and means to inflict more harm to your people's lives and properties, and we will not stop unless we get justice for the countless Muslims lives and properties that you people have destroyed."
Abu Sayyaf, founded in the early 1990s, is waging a violent bombing and kidnapping campaign against the central government in Manila.
The US has included the group in its list of "terrorist" organisations, saying it has links with Osama Bin Laden's al-Qaeda network.
It is best known for a series of kidnappings of Western nationals, and has also been blamed for the bombing of a passenger ferry in Manila Bay in February 2004 which resulted in the deaths of more than 100 people.
Regional police chief Antonio Billiones said he was still investigating the three incidents on Monday.
"But, we can link the attacks to what is happening in the mountains of Jolo," he said.
Fighting has been going on for a week on Jolo island, between soldiers and rebels thought to be from both the al-Qaeda-linked Abu Sayyaf group and a break-away faction of the Moro National Liberation Front (MNLF).
As a result of the fighting, up to 15,000 people have fled their homes.
On Monday the Red Cross expressed concern for their safety.
"Our problem is that we cannot get into some of these areas for security reasons," a Red Cross official told the French news agency AFP.
Ben Loong, governor of Sulu province, said on Monday that the army needed "one or two more weeks" to crush the uprising on Jolo.
Brigadier-General Agustin Dema-ala, who is leading the military operation, said: "Our troops are closing in. It's just a matter of time."