Pakistani police used rubber bullets and tear gas to subdue a crowd gathered at the Supreme Court house in Islamabad shortly after the country's top judge arrived for a controversial court hearing, police and witnesses told CNN.
In anticipation of Pakistan's Supreme Court Chief Justice Iftikhar Mohammad Chaudhry arrival, the government arrested opposition politicians and attempted to restrict media coverage, authorities said.
The crackdown came as Chaudhry was to hear the government's charges against him.
Last week Pakistani President Pervez Musharraf suspended Chaudhry, accusing him of misusing his powers.
Chaudhry was subsequently placed under house arrest -- outraging many Pakistanis, as well as attorney, who staged protests throughout the country.
Chaudhry was appointed to the court by Musharraf in 2005, but recently started asserting judicial independence from the government in a number of cases involving the disappearance of terror suspects and human rights activists.
CNN's Syed Mohsin Naqvi in Lahore said Pakistan's media regulatory authority issued written and verbal warnings to local media outlets demanding that journalists not report on Friday's judicial proceedings.
Police also sealed off the city's main entrance points and restricted access to parliament.
In the days leading up the to hearing, police sources also told CNN the government made approximately 400 arrests.
Early Friday morning, police raided the houses of numerous members of parliament, arresting about 20 members and placing key opposition leader Qazi Hussain Ahmad under house arrest.
Former Pakistani President Muhammad Rafiq Tarar was also arrested.
In addition, police picked up 40 lawyers traveling to the capital.
On Thursday, the government pulled the plug on a leading prime-time television program because of what it deemed to be negative coverage of Musharraf's fight with Chaudhry, senior government sources said.
Kamran Khan, who hosts a show on the Geo TV network, told CNN that he had been banned from doing his show as of Thursday. Sources told CNN that other shows are likely to be banned as well.
Musharraf's critics accuse him of intimidating the judiciary ahead of crucial elections and a vote in parliament to extend his rule later this year.
Musharraf seized power in a military coup more than seven years ago, but under Pakistan's constitution, he has to surrender his position as army chief unless he gets the backing of the Supreme Court, headed by Chaudhry.
Musharraf is believed to want to remain in military uniform to bolster his standing in the country, but his popularity is waning because of his support for the U.S. war on terror.
He has also been criticized by some U.S. lawmakers and Afghanistan's President Hamid Karzai for not doing enough to crack down on Taliban and al Qaeda remnants in the mountainous tribal areas of western Pakistan.
Karzai blames Musharraf for allowing the militants to cross the border and wage attacks in Afghanistan.