At about 10pm, the FRU engaged the crowd gathered in an open field in front of a shophouse that is being used by PKR as its operation centre for the April 7 by-election.
The opposition leader and other Pakatan Rakyat leaders were holed up in the operation centre until nearly 11pm as police continued breaking up the crowd outside.
According to PKR’s Selangor executive councillor Dr Xavier Jeyakumar, those arrested include fellow party member Zamri Yusuf who is a Senator from Kedah and Anwar’s chief of staff Ibrahim Yaacob.
He added that the crowd of thousands dispersed into nearby housing areas with the FRU giving chase as they continued to fire tear gas.
Others arrested include aides to Kedah Menteri Besar Datuk Seri Azizan Abdul Razak and S Manikumar, the candidate for the Bukit Selambau by-elections.
According to PKR party workers, about 50 people were detained and taken to the police headquarters in Kuala Muda.
“I am so angry that the FRU used water cannons and tear gas on 5,000 people gathered to hear DSAI speak,” Dr Jeyakumar stated.
He also told The Malaysian Insider that there were rumours that the authorities wanted to detain the PKR de facto leader.
Other PKR sources have also told The Malaysian Insider of such rumours since last week when Anwar first hit the campaign trail for the three simultaneous by-elections in Bukit Selambau, Bukit Gantang and Batang Ai.
Anwar did however manage to leave the scene after 11pm after being escorted by his security personnel to his car.
Jeyakumar also said that many were injured in the attack as the crowd were ambushed from the back.
The police and FRU also dismantled the tents, confiscated the rostrum and all the PA equipment from the site.