KARACHI, Pakistan -- The government announced a security operation against sectarian death squads in the western city of Quetta on Tuesday, four days after a sectarian bombing killed at least 89 people and led to unusually sharp criticism of the powerful military and its intelligence agencies.
Prime Minister Raja Pervez Ashraf vowed to target the extremists behind Saturday's bombing, which killed dozens of women and children, and was squarely targeted at a neighborhood in Quetta where Hazara, minority Shiites, are concentrated.
On Tuesday evening, after talks with government officials, Hazara leaders called off countrywide protests that highlighted the failure of Pakistan's civilian and military authorities to stem the rising tide of sectarian bloodshed.
Grieving Hazaras, who had demonstrated in the streets of Quetta beside the coffins of bombing victims, agreed to abandon the symbolically powerful protest and bury their dead.
But participants in the Quetta sit-in and other cities refused to end their protest, continuing to demand that soldiers be deployed in the city to provide protection to the Hazaras.
Qamar Zaman Kaira, the Pakistani information minister, told reporters that targeted operations against militants started in Quetta overnight on Monday, resulting in the killing of four militants. At least 170 people were detained and a huge cache of weapons was recovered.
Still, pressing questions remained about the government's ability to crack down on sectarian extremists who, in Quetta as in other parts of the country, appear to operate with impunity. The target of the operation announced by Mr. Ashraf is presumed to be Lashkar-e-Jhangvi, a notorious sectarian group that claimed responsibility for Saturday's attack as part of a violent campaign that has lasted decades.
Lashkar militants bomb and shoot Shiites, whom they believe to be Muslim heretics, across Pakistan, although in Baluchistan Province, which includes Quetta, they concentrate on Hazaras, who immigrated from Afghanistan over a century ago and whose members have distinctive Central Asian physical features.
Mr. Ashraf fired the police chief of Baluchistan Province and replaced him with Mushtaq Sukhera, the former head of counterterrorism operations in Punjab Province. Unusually, though, the brunt of the criticism has focused on role of the military and its powerful intelligence agencies.
In the Senate on Tuesday, Farhatullah Babar, a spokesman for President Asif Ali Zardari, accused some extremists in Baluchistan of having received "clandestine support" -- a veiled reference to allegations from human rights groups that the security forces have turned a blind eye to Lashkar-e-Jhangvi in return for the militants' help in quelling a nationalist revolt in Baluchistan.
Earlier, the governor of Baluchistan Province, Zulfikar Ali Magsi, who has been in charge of Baluchistan since the federal government dissolved the provincial administration last month, accused the intelligence services of being "too scared" or "too clueless" to chase down the extremists.
Mr. Babar, pointedly noted that two Lashkar-e-Jhangvi leaders, whom he named as Usman Kurd and Daood Badini, had mysteriously escaped jail in a military-controlled part of Quetta about four years ago.
The military has strongly denied accusations of collusion with the killers, pleading that its forces are already thinly stretched across Baluchistan. Nonetheless, Pakistanis across the country have been become increasingly alarmed at the strength of Lashkar-e-Jhangvi.
The group's leader, Malik Ishaq, travels freely around Pakistan, making speeches and whipping up sectarian hatred. In Baluchistan, Lashkar operates freely from Mastung, a small town south of Quetta, from which most of the attacks are believed to emanate.
Mr. Ashraf, meanwhile, sent a six-member delegation of lawmakers, led by Mr. Kaira, the information minister, to hold talks with Hazara leaders in Quetta.
In Lahore, a spokesman for the Majlis-e-Wahdat ul Muslimeen, a Shiite lobbying group, said the hand-over of Quetta from civilian to military control was a central demand of the protesters.
"We want the army to maintain peace and stop the massacre of Shiites," said the spokesman, Mazahar Shigri.
Salman Masood contributed reporting from Islamabad, Pakistan, and Waqar Gilani from Lahore, Pakistan.
This article originally appeared in The New York Times.