According the NGO Suaram, Hii was nabbed at the entrance of the Pudu LRT station at 10.30am after holding a protest in the city centre.
When contacted, a Dang Wangi police officer in charge of those in custody refused to provide any information, and hung up before he could be asked for the name of the officer investigating the case.
Hii, 60, contested in the recent Sarawak state election, as an independent candidate for the Bukit Assek seat.
He was arrested one day before the Bersih 2.0 rally for holding a one-man protest in Petaling Street, and was released after being held for five days.
Hii, who claimed that the police slapped him nearly 10 times while he was held in their custody, has taken his case to the Human Rights Commission (Suhakam).