6 injured in suicide bombing at police HQ in Indonesian city of Medan

Indonesian police at their headquarters in Medan after the suspected suicide attack AFP/ATAR

The motive for the attack was not immediately clear, but Indonesia has suffered a resurgence in homegrown militancy in recent years, with some attacks targeting police.

The blast happened around 8.45am local time (0145 GMT) at the police compound in Medan during morning roll call.

"For now, we believe he was a lone wolf," national police spokesman Dedi Prasetyo told reporters in Jakarta.

"The initial of the perpetrator is RMM, he is 24 years old, he was born in Medan and he is a student, and more of his identity is still under investigation by Densus 88."

Six people were injured - four police officers, a part-time worker and a member of the public.

The victims, who were not seriously injured, were being treated at the North Sumatra police hospital, he added.

The explosion also damaged three police vehicles and one private vehicle.

Prasetyo said the bomber managed to enter the police headquarters during a security check, when he "sneaked in" by "making use" of a moment where a large crowd was entering the compound.

"Then, before he managed to perhaps get to his target, the bomb exploded at the car park."

Kompas TV reported that many people were applying to get clearance letters from the police - a requirement to join the civil service which is currently open for admission.

The attacker - whose identification listed him as a student - wore an explosive device on his body, with authorities recovering nails, an on-off switch button, cables and body parts, Prasetyo said.

A bloody corpse lying in the compound's parking lot appeared to have been blown apart.

Police said the attacker was active on social media, while CCTV footage showed him entering the compound wearing a uniform worn by drivers of a popular ride-hailing service.

Prasetyo said police are hoping to establish the bomber's identity by collecting his fingerprints, as well as the type of bomb used through forensic analysis.

"Once we know the bomber's identity, we will investigate if he was part of the JAD (Jamaah Ansharut Daulah) network or if he was a lone wolf," he said.

"WE'RE ON ALERT"

In August, authorities shot and arrested a militant who attacked officers at a station in Indonesia's second-biggest city Surabaya, while in June another was seriously wounded when he tried to blow himself up outside a police building on Java island.

Last month, the country's leader Joko Widodo ordered beefed-up security measures after two militants from an Islamic State-linked terror group stabbed his chief security minister. He survived the attack.

The pair were later identified as members of JAD, an extremist network loyal to IS and responsible for several previous attacks - including deadly suicide bombings at churches in Surabaya last year.

Television broadcast images of people rushing out of buildings around the headquarters.

An eyewitness told Kompas TV: "I was queuing to apply for a clearance letter. Suddenly there was an explosion."

"It was strong - I felt like I was being lifted from the ground.

"It sent debris flying. There was white smoke," she said, adding that people were running out in a stampede.

Another eyewitness told Metro TV: “I heard a loud bang! I was around 20m away. Police immediately secured us and took us to a safe place.”

In Singapore, the Ministry of Foreign Affairs (MFA) issued a statement early on Thursday (Nov 14) condemning the act of terror at the Police Headquarters in Medan, North Sumatra.

MFA said there was no report of any Singaporean affected by the incident, and wished those who were injured a speedy and full recovery.