MANILA — The first bombs exploded outside two Catholic cathedrals on the restive southern Philippine island of Mindanao. They were followed by a series of blasts two days later that raised the toll to 12 dead and 100 injured.
The wave of violence last week in this religiously divided and politically troubled archipelago has made residents skittish even in Manila, the capital some 500 miles to the north, where a bomb damaged a government office in June and several others were found.
President Gloria Macapagal Arroyo has beefed up an anti-terrorist command center and troops have been placed on high alert. Bomb-sniffing dogs patrol the airport and weapons checkpoints have sprung up throughout the metropolitan area of 12 million residents.
So far, no group has taken responsibility for the attacks -- fueling speculation in the press, on the streets and among opposing government factions.
Everyone seems to agree on this: Most every group is suspect.
Each day the newspapers offer a new scenario: The bombs were placed by extortion groups aided by ex-military officials. They're the work of communist insurgents or one of several Islamic separatist groups operating on Mindanao, where scores of bombs have either exploded or been uncovered this year.
The Christians blame the Muslims, and vice versa. Others blame opposition party spinoff groups. Still others blame Arroyo, claiming a farfetched scheme that would enable her to declare martial law.
"I don't think there's a master puppeteer for all of these bombings. But like most things when it comes to such violence, that's pure speculation," said Ricardo Blancaflor, executive director of the government's anti-terrorism council.
Many regard the violence as a prelude to Arroyo's State of the Nation address scheduled for this month.
Arroyo canceled a trip to Mindanao after the attacks there and instead convened a conference among her security advisors In Manila. After the meeting, officials said they believed the Mindanao bombings were test missions for insurgents who recently finished their training here.
The U.S. Embassy in Manila has advised Americans to avoid travel to the southern island, said duty officer Michael Ho. Philippine officials said the attacks were on the agenda for discussion with CIA chief Leon E. Panetta during his one-day visit Sunday.
Truce talks recently broke down between the government and members of the Moro Islamic Liberation Front, which has waged a decades-long battle for self-rule in the southern Mindanao region.
Abu Sayyaf, an Islamic militant group that has been linked to Al Qaeda, has previously been blamed for a string of bombings and kidnappings, most recently of three Red Cross workers in Mindanao. The last of them, an Italian, was released Sunday.
The government is also battling a group of communist insurgents called the New People's Army that rejects Manila's rule.
"When a bomb goes off in the Philippines, the list of usual suspects is a long one," Blancaflor said. "We have the world's two most active secessionist groups as well as the world's oldest political insurgency. Not to mention other combatants."
Meanwhile, several newspapers and former President Joseph Estrada have blamed Arroyo, saying that the unrest could give her an excuse to impose martial law.
Blancaflor dismissed that theory. "It's no different from barbershop talk," he said.
On Tuesday, two bombs exploded in separate incidents on Mindanao. Six people died and about 40 were hurt by the first one, which rocked a gasoline station.
Two hours later, another bomb exploded near a pawnshop on a different part of the island, injuring 13 people, including three soldiers.
The blasts came two days after bombs exploded outside the two Catholic cathedrals in Cotabato city, killing six, including an infant.
Church officials blamed Muslim factions, and priests in Mindanao were advised against traveling in crowds.
"Let's spare our civilians. Don't involve them in this. Do not make them part of the collateral damage," Cotabato Auxiliary Bishop Jose Colin Bagaforo was quoted as saying in the Philippine Star newspaper. "It is an act of brutality to involve innocent civilians in the ongoing conflict between the military and the Muslim rebels."
Many in the Muslim community expressed outrage over being singled out for every bomb.
Outside the Manila Golden Mosque, Arabic music played as vendors sold Korans and head scarves under an intense midday sun. Bobby Limbona had a scowl on his face.
"Every time a bomb goes off, they blame the Muslims," he said. "Life isn't always that simple. Sure, this could be the work of misguided Muslims. But it could be misguided Catholics too."
In an interview with The Times, Philippine National Security Advisor Norberto Gonzales said the government was frustrated by the attacks, whether they were the work of "political anarchists or religious fundamentalists."
"How do we stop this? We have to start with talks with the major organized groups and hope the word filters down," he said. "Our problem in the Philippines is not simple."
Gonzales said he expected more bombings before Arroyo's speech July 27. "Militants no longer believe that rallies work," he said. "They want to get their message across, so they might resort to more gimmicks like bombs."
A photo gallery on Manila's teeming Muslim neighborhood of Quiapo.