Shops and fuel stations were shut and public transport idled after the city's dominant political party, the Muttahida Qaumi Movement (MQM), announced a day of mourning in response to the latest violence in the country's financial hub.
"Of the 80-85 people martyred, most of them are innocent people," Interior Minister Rehman Malik told reporters. "Very few are politically affiliated people."
He added 89 people had been arrested since last night for involvement in violence.
A police source said 18 people had been killed since midnight.
"We have issued orders to the security forces to shoot anyone involved in violence on the spot," Sharjeel Memon, the provincial information minister, told Reuters.
"In addition to the police and Rangers, another 1,000 personnel of the Frontier Constabulary will be deployed in the city to control the violence," he said, referring to another paramilitary force.
"Thirty-seven people were killed yesterday alone," Memon said.
Most of the casualties over the past three days were reported in the city's western Qasba Colony and adjoining areas -- a multi-ethnic, lower middle class neighbourhood.
But slowly, trouble is spreading to other parts of the city.
Firing could be heard in several areas on Friday, and in some spots residents burned tyres and threw stones at the few passing vehicles on the street.
Huddles of people waited in vain at bus stops for public transport and most shops were closed. Every few kilometres, a small group of lightly armed police stood a wary watch.
Pakistan Prime Minister Yusuf Raza Gilani appealed for peace, calling for the country to unite against the city's violence.
Copyright Reuters, 2011