No official reason was given but the party, the Pakistan Muslim League-Nawaz (PML-N), says it is an attempt to stifle its ability to launch street protests.
A police official, who asked not to be identified, said more than 100 PML-N workers had been detained.
“We received instructions to take prominent PML-N activists from their areas to avoid a law and order problem,” the official said.
The crackdown on the PML-N, whose leaders have accused the military of attempting to destabilise the party, comes a day before the party founder, ousted prime minister Nawaz Sharif, is due to return to Pakistan where he faces arrest.
Muhammad Mehdi, the party’s media co-ordinator, said that nearly 500 workers had been detained in a “massive crackdown”, including raids on the homes of a number of the party’s local councillors.
PML-N members have said the crackdown on workers who handle street level organising will make it harder for them to stage rallies and protests on Sharif’s return, when he will challenge the verdict and sentence against him.
A Pakistani accountability court on Friday sentenced Sharif in absentia to 10 years in prison for corrupt practices linked to his family’s purchase of upscale London flats.
Sharif has denounced the court proceedings as politically motivated and a judicial witch-hunt, often suggesting the military was to blame.
Sharif has also said the military’s intelligence wing, the Inter-Services Intelligence Agency, is intimidating his party's candidates to switch loyalties or run as independents, ahead of the July 25 poll. - Reuters/African News Agency (ANA)