Dozens of riot police armed with water cannons barged into a hall where Anwar's National Justice Party (Keadilan) was holding a meeting late on Saturday, Keadilan youth chief Ezam Noor said.
"They asked us to disperse and when we refused, they switched off the lights and started pushing people out and even hitting some of us," he said.
Several of the 1000-strong crowd, which included women and children, were injured, he added.
At least four party leaders were arrested and held overnight, only to be released on Sunday morning with no charges filed against them, Ezam said.
"These are very repressive moves and it's clear Prime Minister Abd Allah Ahmad Badawi is trying to ensure the Anwar Ibrahim issue is not highlighted again especially with the elections coming up," Ezam said.
"(Prime Minister) Abd Allah is panicking, he is afraid. Just because we are touching on the Anwar issue, the police have been ordered to harass us Gestapo-style, even though we are holding the rally in our own party premises"
National Justice Party leader
"Abd Allah is panicking, he is afraid. Just because we are touching on the Anwar issue, the police have been ordered to harass us Gestapo-style, even though we are holding the rally in our own party premises," he added.
"He's talking about democracy and reforming the police all the time, but it does not mean anything when the police are harassing us. We are a registered political party. These are double standards," Ezam said.
Perak police have refused to confirm any details.
Ezam said Keadilan, headed by Anwar's wife Wan Azizah Wan Ismail, and the Free Anwar Movement would continue as planned with a cross-country convoy of up to a hundred vehicles handing out leaflets calling for Anwar's freedom.
Anwar (L) with former premier
The month-long event is due to culminate in a mass rally in Anwar's home state of Penang on 14 February.
The planned demonstrations will be the first challenge for Abd Allah, who took over from Mahathir Muhammad when he retired on 31 October after 22 years in power.
Former heir-apparent Anwar was sacked by Mahathir in 1998 and later sentenced to 15 years in prison for corruption and sodomy in what he says was a move to prevent him from making a challenge for the premiership.
His supporters wanted him freed on bail before general elections due this year, but the Court of Appeal last week dismissed his application.