9/3/2106: A previous version of this story stated that a doctor, Leopoldo Vega, spoke to Al Jazeera by phone about the victims of the explosion. That was incorrect. He made the statement during a news conference.

The Philippine government has blamed the armed Abu Sayyaf group for a blast that killed at least 13 people in the home city of President Rodrigo Duterte, prompting him to declare a "state of lawlessness".

Duterte told reporters in Davao City on Saturday that he "may invite uniformed personnel to run the country according to my specifications".

He said police and the military will be authorised to conduct searches "in a bid to stop terrorism. 

"This is not the first time that Davao has been sacrificed to the altar of violence," the president said, adding: "It's always been connected with Abu Sayyaf before. They gave a warning. We know that.

"We were ready for this," Duterte said when asked if the attack constituted a failure of intelligence.

Interior Minister Mike Sueno earlier told local radio station DZRH that his office had information about an imminent Abu Sayyaf attack.

"Yes, we expected this already. Two or three days ago, we already had an intelligence (report) on this." 

Another radio station also reported that Abu Sayyaf spokesman Abu Rami had confirmed that attack.

'Civil liberties still stand' 

Richard Heydarian, a professor of political science at Manila's De La Salle University, told Al Jazeera that a "state of lawlessness" is not the same as martial law, whereby certain civil liberties are suspended.

"What it means is that there will be more police presence; more checkpoints; the military could be involved and have more coordination with the police and, if necessary, impose a curfew. But basic civil liberties will still stand.

"One thing we're still not certain about is whether it is going to be a nationwide state of lawlessness, or only for Davao, because we've been getting mixed signals from different offices of the president."

The blast took place on Friday night at a night market in Davao, 960km south of the capital, Manila.

The explosion occurred close to the high-end Marco Polo hotel, which is popular with tourists and business people, city spokeswoman Catherine de la Rey told AFP news agency.

Regional police chief Manuel Guerlan told Reuters news agency that a ring of checkpoints had been thrown around the city's exit points.

Student John Rhyl L Sialmo told Al Jazeera that the explosion happened around 10:30pm local time (4:30 GMT).

"We were inside one of the university buildings when we heard the loud explosion," said Sialmo, a student at Ateneo de Davao University, located across the site of the blast. 

"There were so many people, because it was a night market and also because it's a Friday," Sialmo said, adding that "the rescuers had to use improvised bandages on the victims".

A doctor from the Southern Philippine Medical Center in Davao City, said that all those who died had "multiple shrapnel injuries".

"All of the wounds examined were shrapnel type on different parts of the body," D Leopoldo Vega told reporters in a news conference.

War on drugs

The Philippine president was in Davao, but was safe and at a police station after the explosion, his son Paolo Duterte, who is vice mayor of the city, told Reuters news agency.

Duterte is hugely popular in Davao, having served as its mayor for more than 22 years before his stunning national election win in May, garnered from the popularity of a promised war on drugs.

READ MORE: Death toll in Duterte's war on drugs

His election has prompted a steep rise in drug-related killings, with more than 2,000 people killed since he took office on June 30, nearly half of them in police operations.

Davao is located in Mindanao, a large southern island beset by decades of armed rebellion by Muslim groups. The region is also home to Abu Sayyaf, a rebel group loosely linked to Islamic State of Iraq and the Levant (ISIL, also known as ISIS) and notorious for making tens of millions of dollars from kidnappings.

There was no immediate claim of responsibility.

However, Davao itself is largely peaceful and Duterte has been credited with transforming it from a lawless town to a southern commercial hub for call centres and offshore business processing services.

Source: Al Jazeera News and agencies