JAKARTA - A 24-year-old "lone wolf" suicide bomber died and six people were injured when he blew himself up at the police headquarters in the Indonesian city of Medan on Wednesday (Nov 13), national police spokesman Dedi Prasetyo said.

In a media briefing on Wednesday afternoon, Mr Dedi said the Medan-born man, initialled RMN, was identified based on fingerprints.

"The attacker has been identified. Based on our preliminary investigation, he was a lone wolf," Mr Dedi told reporters.

"On the type of bomb, we are still investigating. We found a 9-volt battery, metal sheet, nails in different sizes, wirings, an on/off switch."

The bombing happened on Wednesday morning when the perpetrator allegedly walked into the compound at around 8.40am local time (9.40am Singapore time) after a police morning briefing and then blew himself up in a parking lot near a building where certificates of clearance, known as SKCK, are processed.

"We still don't know if it was a high explosive. The team is working with Inafis (Indonesia Automatic Fingerprint Identification System) and forensic laboratory to examine the crime scene," another national police spokesman Inspector-General Muhammad Iqbal said earlier.

He added that the suicide bomber was killed, while the six people - five police officers and one civilian - were injured and several vehicles were damaged.

All the victims were taken to a police hospital, local media reported. Medan is the provincial capital of North Sumatra.

The police and the anti-terrorism squad Special Detachment 88 (Densus 88) are investigating the incident, including looking into which group might be behind the attack, Insp-Gen. Iqbal said.

Singapore condemns the act of terror, the Ministry of Foreign Affairs said in a press statement issued on Wednesday night, adding that it wishes the injured a speedy and full recovery. There were no reports of any Singaporeans affected by the incident, the statement said.

Police are investigating three members of the suicide bomber's family, including his cousin, and have begun looking into the bomber's activities after finding nothing when ransacking his parents' house in Sei Putih Barat village in the Medan Petisah sub-district in Medan, said North Sumatra police spokesman Tatan Dirsan Atmaja.

RMN used to be a driver at a ride hailing service, he added.

"His affiliation after quitting from the ride hailing service is still unknown," he told reporters in Medan.

RMN's cousin, Maya, who goes only by one name, said that the man had moved to parents-in-law's house in another sub-district after getting married last year. She described him as a "nice guy" who once worked as a mobile grilled meatball vendor.

A number of Indonesian television channels showed footage of people rushing out of buildings around the headquarters.

Eyewitnesses told local media they heard a loud explosion and saw puffs of white smoke as they rushed out of the building.

A witness named Lila Mayasari told MetroTV news station that she was queueing to get her paperwork done inside the police headquarters when she heard a loud blast.

"There was an explosion. I felt as if I was lifted off the ground, like there was an earthquake. It was loud and then I saw white smoke. I panicked and shouted 'Bomb!' Everyone panicked and started running," she said.

Another witness, Mr Jones, told MetroTV that he saw a brown-skinned man, about 1.7m tall, in the parking area at the headquarters.

"He carried a bag... and I was suspicious of his facial expression... (as) if he wanted to commit a crime," Mr Jones said, adding the man was wearing a jacket belonging to a ride-hailing service.

A police source who refused to be named said the perpetrator walked into the compound after a briefing there, and one of the police officers, Police Commissioner Abdul Mutolip, tried to chase the man, who was clad in a ride-hailing service jacket and made "suspicious movements".

The man exploded the bomb at the location before Com Abdul could reach him, the source said.

The source also added that splinters could be found near a food stall about 200m from the police headquarters.

The police, with the assistance of a sniffer dog, were trying to find explosive materials that might have spread in the location, MetroTV reported.

In recent years, radicals, some tied to the ISIS-inspired militant group Jamaah Ansharut Daulah (JAD), have targeted police in a series of attacks.

The latest attack comes a month after a suspected militant stabbed and wounded Mr Wiranto, Indonesia's former security minister, who uses one name.

In August, Indonesian authorities shot and arrested a suspected militant who attacked police officers at a station in the country's second-biggest city, Surabaya.

In June 2017, two terrorists brazenly walked into North Sumatra's police headquarters, also in Medan, and killed a policeman with knives. The attackers wanted to steal guns from the police for use in even bigger atrocities.

On Sept 22, 2010, at least 10 militants killed three of the five officers on duty in a bloody assault at around 12.45am on the remote Hamparan Perak police station in the Deli Serdang regency in North Sumatra. This came after anti-terror police launched major raids on the militant groups in the region who were suspected of being behind a series of bank heists, including the CIMB Niaga bank branch in Medan, to raise money to fund their terror activities.

Additional reporting by Adi Prasetia in Medan