A man suspected to be in his late 20s detonated explosives strapped to his body at a mosque in Cirebon, West Java province, where many police were performing Friday prayers.
"We're increasing security in police headquarters across the country regarding people coming in and out. But we are doing this subtly," Indonesia police spokesman Anton Bachrul Alam told AFP.
At least 26 people were injured by the low-level explosion, including Cirebon's police chief, and the attacker was killed instantly.
"We're still trying to identify the bomber, find out his background and his link. Hopefully we can soon announce his identity," he said.
Alam said that the body of the bomber had been brought to a police hospital in Jakarta for identification.
The last significant bombing in Indonesia was carried out by two suicide bombers who killed seven people at two luxurious Jakarta hotels in July 2009.