Several masked men attacked the Riau Police headquarters at around 9 a.m. on Wednesday with sharp weapons and firearms, killing one police officer and injuring another.
The attack is the latest in a spate of attacks in the country.
Suddenly the militants exited the vehicle and immediately stage strikes with swords against policemen, provincial police spokesman Sunarto said.
Separately, Sunarto said police are still searching for more attackers.
"Three officers were injured and one later died in hospital", said local police chief Nandang, who goes by one name.
Media said one attacker may have had a bomb strapped to his body but police did not immediately confirm the reports.
Just two days ago, on Monday, 10 people were injured in a suicide bombing as two motorcycles drove into a checkpoint at a police station in the Indonesian port city of Surabaya.
Police shot a militant and arrested at least 13 others in a series of raids following the Surabaya attack.
This week's bloody violence is putting pressure on lawmakers to pass a stalled security law that would give police more power to take pre-emptive action against people suspected of planning terror attacks.
It was not clear if Wednesday's incident was linked to the earlier attacks in Surabaya, Indonesia's second biggest city, which have been claimed by ISIS.
State news agency Antara said two journalists who had been at the police headquarters were also hurt in the attack.
"We are now checking the minivan and the body of the assailants", said Riau Police spokesman Adj. Sr.