A 24-year-old university student blew himself up outside police headquarters in the Indonesian city of Medan on Wednesday, wounding six people, just a month after an Islamist militant attacked a former security minister.

Axar.az reports citing Reuters.

National police spokesman Dedi Prasetyo said the student was a “lone wolf” suicide bomber, although authorities were still investigating whether he had links to any militant groups.

Indonesia, the world’s most populous Muslim-majority country, has suffered a resurgence in homegrown militancy in recent years, with police frequently the target of attacks.

Prasetyo said four police officers and two civilians, one of whom was a police employee, were wounded by the blast in a car park at Medan police headquarters shortly before 9:00 a.m.(0200 GMT).

“All pieces found at the scene will be tested by a forensic lab to determine the type of bomb,” Prasetyo told a news conference, noting that nails, cables, a switch button and the suspect’s body parts had been recovered.

Indonesia’s anti-terrorism unit, Densus 88, was investigating whether the bomber had any links to a radical group like the Islamic State-inspired Jamaah Ansharut Daulah (JAD), which has carried out a series of attacks in the country, he said.