“Now, the M.Q.M. cannot close the city,” said one gas station manager. “It seems the armed workers have gone underground due to the ongoing operation.”

The M.Q.M. said that since the start of the Rangers crackdown, at least 54 of its workers have been killed in extrajudicial killings and the whereabouts of 231 activists are not known. The police and officials with the Rangers have denied those accusations.

In one case, a 40-year-old M.Q.M. activist and city employee named Sanaullah was arrested by law enforcement agencies on March 31 last year. His body was found the next day in a nearby town, and his widow, Nida Fatima, is convinced that he was summarily killed by the authorities. “If my husband was involved in any crime, he should’ve been presented in front of the court,” she said in an interview.

Although overall killings have gone down significantly in Karachi, the Human Rights Commission of Pakistan, an independent rights monitoring group, says there has been a large increase in the number of killings by the police and paramilitary force — and that not all can be explained away as shootouts with determined militants. The group says that at least 430 people were killed in shootouts with the law enforcement agencies in the first nine months of 2015.

Asad Iqbal Butt, an official with the human rights group, said that given the vast increase in detention and investigation powers given to the security agencies by recent legal changes, the killings are even more inexplicable. “After being empowered to keep a suspect in custody for 90 days for interrogation, there is no excuse for such killings,” Mr. Butt said.

Several law enforcement officials, however, insist that the majority of such so-called encounter killings have been with the Taliban and other militant or criminal syndicates that have no compunction against shooting at the police or the Rangers.

“We are fighting with well-organized militant groups that have killed more than 65 law enforcers only this year in ongoing operations,” one senior police official said.