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.

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.

Read more: Reuters