JAKARTA, May 16 (Xinhua) -- The perpetrators in the sword attack on the police headquarters of Indonesia's Riau province on Wednesday have links with the Islamic State (IS), a police officer said.

Four sword-wielding assailants were shot dead with another nabbed, and one police officer was killed in the attack, National Police Spokesman Inspector General Setyo Wasisto said.

The attackers were members of the Negara Islam Indonesia (NII) which is affiliated with the IS group, the spokesman said.

"This group has been loyal to the IS," he told a press conference at the national police headquarters.

During the assault, the militants also wounded two police officers and hurt two journalists, according to him.

A minivan with four to six people onboard intruded the compound of the headquarters at 09:00 a.m. Jakarta time, but it was halted by other cars. The militants then unexpectedly exited the minivan and staged strikes with swords against policemen at the spot, spokesman of provincial police Sunarto said.

Two policemen were injured by the sword attacks and another was killed after being hit by the minivan which was trying to escape from the compound of the headquarters, he added.

Previously Police chief of Riau province Inspector General Nandang said that a total of eight militants with a white minivan staged the attacks.

The militants also rampantly shot at the headquarters, according to national police spokesman Senior Commissioner Muhammad Iqbal.

The attack followed multiple terrorist strikes recently in the country, including the riot in a jail in the capital last week, suicide bombings in three churches on Sunday in Surabaya city, the provincial capital of East Java, and a suicide bombing in the police headquarters in the city, which left at least 28 dead with dozens injured.

The incidents were followed by a series of gunfight between the police and terrorists in the province and North Sumatra province that killed three militants, according to the police.