At least 11 people, including soldiers and civilians, have been killed and seven others wounded after a bomb exploded in a van in the island province of Basilan in the southern Philippines, the military said.

The explosion occurred as a van with a single passenger approached an army checkpoint in Lamitan City on Tuesday.

“The van was stopped at the checkpoint and when our troops were approaching it, the driver panicked and detonated the improvised explosive device (IED) inside,” anti-terrorism task force commander Colonel Fernando Reyeg, told DPA news agency.

A suspected bomber, a soldier, five paramilitaries and four civilians, including a mother and her child, were among the dead, Reuters news agency reported, citing an army spokesman. The impact of the blast went as far as 50 metres.

There is no claim of responsibility yet, but the military and the provincial governor suspect the armed group Abu Sayyaf is behind Tuesday’s attack.

Abu Sayyaf is accused of being allied with the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group.

Presidential spokesperson Harry Roque Jr vowed to bring the perpetrators of the “brazen attack” to justice.

“We condemn in the strongest possible terms the latest terrorist attack in Basilan perpetrated in violation of our laws,” he said in a statement.

‘Tighter security’

Southern Philippines, especially the Mindanao region, has been on high alert since ISIL-linked fighters laid a five-month long siege in Marawi City last year.

The region is currently under martial law, which was declared by President Rodrigo Duterte in May 2017, and later extended by Congress to the end of 2018.

Basilan is a stronghold of the Abu Sayyaf group, which has been blamed for some of the worst attacks in the Philippines, as well as high-profile kidnappings for ransom.

“This has been one of the rare times that an attack has happened in Basilan over the past few years,” said Al Jazeera’s Jamela Alindogan, reporting from the capital, Manila.

“There had been relative peace there since the former leader of the Abu Sayyaf group was forcibly pushed out of Basilan and he moved to Marawi to launch a war there against the military,” she added.

Following Tuesday’s explosion, a “tighter security protocol” and “intense intelligence operations” are expected in Basilan, which is about 30 minutes by boat from Zamboanga, one of Mindanao’s main cities, Alindogan said.

Last week, Duterte signed a landmark law granting autonomy to the Muslim-majority region of Mindanao aimed at ending a decades-long armed rebellion.

The Moro Islamic Liberation Front expressed confidence early this week that the passage of the Bangsamoro Organic Law would soon end the decades-long Muslim rebellion in the south of the mainly Catholic Philippines.