An explosion was heard outside the police headquarters in the Indonesian city of Medan in North Sumatra on Wednesday morning (local time).
A police spokesman said the explosion is suspected to be a suicide bombing, according to Reuters.
The spokesman added that the suspected suicide bomber had died in the attack. He said some police officers were wounded in the blast that occurred at 8:40 a.m. local time.
A number of Indonesian television channels showed footage of people rushing out of buildings around the headquarters.
The Islamic State (ISIS) claimed a suicide and gun assault in Jakarta in 2016 that left four civilians dead, and was the first major terror attack in the country for seven years.
Later, Indonesia detained 14 people, including several children, who allegedly tried to travel to Syria to join jihadist groups.
A year earlier, Australia warned that ISIS is working to boost its presence in Indonesia with dreams of creating a "distant caliphate" in the world's most populous Muslim-majority country.