Pakistani police detained hundreds of opposition workers on Saturday and banned rallies two days before former premier Nawaz Sharif was due to arrive home to challenge what he calls the 'illegitimate rule' of President General Pervez Musharraf.
"More than 1,500 of our party leaders and workers have been picked up during the last three days in raids across the country," said Ahsan Iqbal, the Information Secretary for Sharif's Pakistan Muslim League (PML-N) party.
Sharif was ousted by General Musharraf in a military coup in 1999, sentenced to life imprisonment for hijacking, tax evasion and treason, and expelled from the country after the remission of prison term in 2000.
However, the Pakistan Supreme Court last month ruled that the former prime minister had an "inalienable right" to return home dealing Musharraf a major blow. Musharraf is already experiencing a sharp slump in his popularity.
PML-N and several other opposition parties have vowed to give Sharif a rousing welcome on his return.
About 300 PML-N workers were held by police in Rawalpindi alone, in a bid to thwart the plan.
The authorities have also imposed a ban on the assembly of five or more persons in public places in the Punjab province, where tens of thousands are expected to take to streets to greet Sharif.
"We cannot be intimidated by such tactics, and our workers will arrive at the airport to greet their leader," Iqbal said.
The security forces will seal all the roads around Islamabad airport to prevent people from gathering there, a senior police official said on condition of anonymity.
The management of several government and private offices have announced a public holiday on Monday, amid fears of violent clashes between law enforcers and opposition workers as the government is planning to arrest Sharif at the airport.
Attorney General Malik Abdul Qayyum said earlier this month that the original sentence against Sharif could be revived, while an anti-terrorism court on Friday issued arrest warrants for his brother.
Shahbaz Sharif, who is due to accompany his elder brother on his return, has been charged with ordering the deaths of five terrorist suspects during his 1997-99 tenure as Punjab's chief minister. He denies the accusations saying accusations were politically motivated.
Meanwhile, Musharraf is holding talks with another exiled opposition leader and former premier, Benazir Bhutto, on a power-sharing deal that is expected to secure his political survival as he seeks another five-year term from parliament around October 15.
Under the agreement, Bhutto wants all corruption charges to be dropped and permission granted to serve a third term as prime minister, in exchange for supporting the president's re-election as a civilian rather than military chief.