Seven people have been killed in Karachi in fresh clashes one day after major political violence hit Pakistan.
At least 34 people died on Saturday in street battles
Troops were deployed across the city, but gunfire was heard in several areas, shops and vehicles were set alight and police were pelted with stones.
Correspondents say there is also a growing ethnic tone to the violence.
At least 34 people died on Saturday in street battles in the city between supporters of the country's president and those of its suspended top judge.
President Pervez Musharraf suspended judge Iftikhar Muhammad Chaudhry in March, but he has since become a focus for protesters trying to end military rule.
Opposition groups blamed the pro-Musharraf MQM party of organising the unrest, but it denied the claim.
Early on Sunday, Karachi police chief Azhar Farooqi described the situation in the city as "very tense".
Pakistan's government on Sunday authorised paramilitary troops to shoot anyone involved in serious violence, Reuters quoted Interior Secretary Syed Kamal Shah as saying.
And the provincial government in Sindh province banned political gatherings, imposing a so-called Section 144 order in an effort to restore order.
The BBC's Shoaib Hassan, in Karachi, says five of those killed on Sunday were kidnapped, then executed. One of them was an MQM worker.
Another two people were tortured and then shot in the head, our correspondent says.
In at least three incidents, Pashtun businesses and shops were targeted, allegedly by the MQM, according to the owners.
The situation on Karachi's streets is said to be "tense"
Meanwhile, in a Pashtun-dominated area in north Karachi, locals attacked vehicles or people dressed in the urban style of the Mohajirs who dominate the MQM.
Opposition groups have called a strike for Monday, against what they describe as the MQM's "terrorist tactics", our correspondent adds.
Meanwhile, the casualty toll from Saturday's violence rose overnight to 39 dead and about 150 wounded, many from gunshots, the Associated Press reported.
Appeal for calm
Mr Chaudhry abandoned plans to address a rally in Karachi on Saturday, finding his way into the city blocked.
9 March: Musharraf suspends Chaudhry for "misuse of authority"
16 March: Violence at pro-Chaudhry rally in Islamabad
3 April: Chaudhry appears before private session of court
6 May: Large rally in support of Chaudhry in Lahore
12 May: Violence in Karachi, ahead of planned rally
Karachi later turned into a battleground as supporters and opponents of President Pervez Musharraf exchanged gunfire on the streets.
Speaking at a mass rally in Islamabad on Saturday night, Gen Musharraf ruled out declaring a state of emergency and appealed to the country to stand united.
"If you really feel sorry over what has happened in Karachi, then stop these protests," he said.
He also blamed "elements who tried to create turmoil by politicising" Chief Justice Chaudhry's suspension.
Since his suspension on charges of "misuse of authority", Mr Chaudhry has become the focus of widespread opposition to the government of Mr Musharraf, who took power in a coup in 1999.
The BBC's Barbara Plett in Islamabad says opposition parties have turned Mr Chaudhry's case into a campaign against military rule.
His supporters say that Mr Musharraf wants the judiciary headed by a lawyer whom he can more easily manipulate.
Our correspondent says tension had been building ahead of the judge's visit when the local authorities announced plans for a counter rally.
But she says the scale of the confrontation took people by surprise.
In the worst violence, MQM supporters and activists from the Pakistan People's Party (PPP) of former Prime Minister Benazir Bhutto fought gun battles for an hour.