Most of the victims were opposition party workers headed for a rally in the volatile southern city of Karachi by Chief Justice Iftikhar Muhammad Chaudhry, who was trapped at the airport by roadblocks set up by Musharraf supporters.

Chaudhry, increasingly a symbol of defiance for those opposed to Musharraf's eight-year military rule, later abandoned his plans to give a speech and flew back to the capital Islamabad.

Musharraf, who was due to address his own rival rally in Islamabad in the evening, ruled out declaring a state of emergency but deployed extra paramilitary troops in armoured cars in Karachi.

Black smoke billowed over the volatile commercial hub as mobs armed with assault rifles and shotguns fought pitched battles in the streets, opened fire on a private television studio and torched dozens of buses and cars.

"At least 30 people died and more than 100 were injured in the violence," Sindh province interior minister Waseem Akhtar told AFP.

"The chief justice is responsible for these deaths, no one else is responsible, no political party is responsible," added Akhtar, a minister for the pro-Musharraf Muttahida Qaumi Movement (MQM) party.

A senior security official said most of the dead were from the Pakistan People's Party of exiled former premier Benazir Bhutto. Other officials said a policeman and a paramedic were among the victims.

The president, a key US ally, dismissed Chaudhry on March 9 over allegations that he had abused his power, turning the judge into a symbol of defiance and unleashing the most serious crisis of the president's eight-year rule since he seized power in a bloodless coup.

Opponents say army chief Musharraf acted unconstitutionally in a bid to neuter the judiciary and make it easier to be re-elected as president by the current parliament before his five-year term runs out in November.

New York-based Human Rights Watch said Musharraf's government and its allies had apparently "deliberately sought to foment violence in Karachi," adding that police stood by as "silent spectators".

An AFP photographer at the scene of the biggest clash said workers from the pro-Musharraf Muttahida Qaumi Movement (MQM) exchanged gunfire for an hour with activists from Bhutto's Pakistan People's Party.

Private Aaj television, which has come under pressure from the government for its allegedly pro-chief justice stance, showed footage of gunmen firing at its office in Karachi and of its correspondents diving for cover.

Justice Chaudhry spent most of the day stranded at Karachi airport because government supporters used trucks with deflated tyres to block all main roads, including those leading to the airport.

"I wanted to address the bar association. But they (the government) want my lawyers to go back and I wanted to go back with my team of lawyers," lawyer Imdad Awan quoted Chaudhry as saying at Karachi airport before flying home.

The MQM -- historically an ethnic party for people who migrated from India after partition in 1947 and which has been implicated in violence here during the 1990s -- held a large counter-demonstration in Karachi to rival Chaudhry's.

Musharraf meanwhile was finally set to make his own show of strength with a rally late Saturday in Islamabad.

Several thousand government supporters, many bussed in from around the country, had gathered outside parliament, although there were far fewer than the 400,000 that the government had predicted.

Musharraf was earlier quoted as saying by the state-run Associated Press of Pakistan that there was "absolutely no requirement and absolutely no environment" for declaring a state of emergency after rumours swept the country.