“They didn’t do much. They only took my details and statement. They were actually quite nice about it,” he told FMT when contacted.

Amir, who is a project coordinator with human rights group Suara Rakyat Malaysia (Suaram), was arrested at about 4.20pm in Jalan Tun Perak while he was walking towards the Masjid Jamek LRT station, Malaysian Insider reported.

He had reportedly led the crowd in a rousing speech denouncing the Trans-Pacific Partnership Agreement and calling for Prime Minister Najib Razak to back down and reject the agreement.

Amir added that he suspected that his arrest had more to do with his exposure of letters from detainees under the Security Offences (Special Measures) Act 2012 (Sosma) last Monday, which claimed that they had been tortured in detention.

Dang Wangi district chief ACP Zainol Samah had said in a statement later today that the arrest was to prevent any “unintended incidents”.

“The Bantah TPPA assembly at Padang Merbok had gone well and nothing untoward had happened.

“However, there was an arrest of a Malay man at Jalan Tun Perak, who was suspected of being part of an anarchy group and he had been arrested by the police in the past. The arrest was made to prevent any unintended incidents,” Zainol had said.