Chaudhry Mohammad Ali, Islamabad's commissioner, said: "We have detained 14 people as a preventive measure. They have given calls for protests and we have fears that they may create disturbances in the coming days."
"Pakistan needs a military leader who can control both civil and possible military extremism"
Creative_person01, Islamabad, Pakistan
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The chairman of Sharif's faction of the PML-N, Raja Zafar-ul-Haq, and acting chief, Javed Hashmi, were among those arrested.
Hussain Ahmed, a central leader of the religious alliance, Muttahida Majlis-e-Amal, was also taken.
"They want to crush every voice of dissent," Hashmi said.
"They have confined me for 30 days, but we will continue to raise our voice for the rights of the people of Pakistan, for democracy and against military dictatorship.
"They want power by the use of force, not by the power of the ballot."
Hashmi, who was freed by the supreme court in August after serving three years in jail on sedition charges, said that his lawyer would challenge the "illegal detention" in court.
Kamal Hyder, Al Jazeera's correspondent in Islamabad, reported on Sunday that Hashmi and several other members of the oppostion had been held under police guard at a parliamentary residence.
The guards were not permitted to allow any of those detained to leave. They were allowed to receive visitors.
Hyder later said that Hashmi had been transferred to a permanent jail.
"Hashmi… has reportedly been taken to a jail in Rawalpindi. That shows the determination of the government to move against the opposition in a very strong way," Hyder said.
Ahsan Iqbal, spokesman for the Pakistan Muslim League (PML-N), who is wanted by Pakistani police and currently in hiding, told Al Jazeera that many of the wanted opposition members were planning on going to court on Monday to "cancel government orders for their arrests".
Ehsan Iqbal, a PML-N spokesman, described the arrests as "cowardly", and said the government was in a panic over the opposition plan to resign en masse from parliament once Musharraf's nomination papers are accepted on September 29.
President Musharraf suspends Chief Justice Iftikhar Chaudhry, sparking riots across the country.
Musharraf's handling of the Red Mosque siege in the capital comes under close scrutiny.
The death of more than 100 students was seen by some as a direct attack on Islam.
Supreme court rules that Nawaz Sharif, a former prime minister, has an "inalienable right" right to return to his country.
Sharif, who was ousted by Musharraf in a coup in 1999, is turned away at the airport.
Failing support for Musharraf has forced him into negotiations with Benazir Bhutto, another former prime minister.
She vows to return to Pakistan after years in exile if Musharraf steps down as army chief.
"They only strengthen our resolve and prove that this is a sham democracy," Iqbal said.
General Musharraf is waiting to hear whether the supreme court will uphold challenges to his plan to get elected while still army chief.
The court is hearing petitions challenging Musharraf's right to retain the posts of president and army chief, the legality of being elected in uniform, and whether he should be allowed to get a mandate from outgoing assemblies.
Musharraf regards the court as hostile since his attempt to sack Iftikhar Chaudhry, the country's chief justice.
Musharraf, who came to power in a 1999 coup, says he will step down as army chief and become a civilian president before November 15 if he is re-elected.
It is expected to issue a ruling next week.
An alliance of pro-democracy parties says it will protest against Musharraf's intention to stand for another five-year term in October 6polls.
On Friday, an opposition alliance said its politicians would resign from assemblies on September 29 to deny the presidential vote legitimacy.
The parties said they would protest on the streets and have asked the supreme court to declare Musharraf ineligible to run for another presidential term.
Anti-Musharraf lawyers said they would blockade the Election Commission to prevent the general from filing his nomination papers.
An intelligence official said the move was in response to the threat to escalate the confrontation with the government and disrupt the election.
The supreme court ruled that Sharif could return to contest elections, but when he did so nearly two weeks ago, the authorities put him on a plane to Saudi Arabia.