Indonesian police officers secure the area for investigation in the house of family who carried the bomb attack at Surabaya's police headquarters in Surabaya, Indonesia, May 15, 2018. (Xinhua/Agung Kuncahya B.)

JAKARTA, May 30 (Xinhua) -- The Indonesian police have arrested four alleged militiants in East Java province in a crackdown against terrorists after a spate of suicide assaults, police said on Wednesday.

Police chief in Probolnggo Senior Commissioner Fadly Samad said the arrests were made on Tuesday night days after the country passed a tougher anti-terrorist law, which allows the police to take pre-emtive actions to prevent terrorist attacks.

"There were arrests on Tuesday evening. But we could not give further details," he was quoted by local media as saying.

During the raid on the hideouts of the alleged militants, the police have seized scores of evidences including, laptop, pipes and a bag, according to him.

Suicide attacks in Surabaya city of East Java and Riau province left 32 dead and dozens of others injured.