Pakistan should "urgently act" to protect minority Shias Muslims from rising sectarian attacks that have killed hundreds this year, Human Rights Watch said Thursday.
"Deadly attacks on Shia communities across Pakistan are escalating," Brad Adams, Asia director at Human Rights Watch, said in the same statement.
"The government's persistent failure to apprehend attackers or prosecute the extremist groups organising the attacks suggests that it is indifferent to this carnage," Adams said.
The rights watchdog said militant groups such as the "ostensibly banned" Lashkar-e Jhangvi (LeJ) had operated with "widespread impunity" across Pakistan while law enforcement officials looked the other way.
LeJ is accused of killing hundreds of Shias after its emergence in the early 1990s. It was banned by then president Pervez Musharraf in 2001.
Adams said the arrest last month of of LeJ leader Malik Ishaq, who has been accused of killing some 70 people, was "an important test for Pakistan's criminal justice system".
Some extremist groups are known to be "allies" of the Pakistani military, its intelligence agencies, and affiliated paramilitaries, such as the Frontier Corps, HRW said.
On September 1, four gunmen riding two motorbikes intercepted a bus near the Hazarganji area of Quetta, the capital of Baluchistan, pulled five Shia vegetable sellers off the vehicle and shot them dead.
On August 30, unidentified gunmen shot dead judge Zulfiqar Naqvi along with his driver and police bodyguard.
Sectarian conflict has left thousands of people dead since the late 1980s.
In one of the bloodiest recent attacks, on August 16 gunmen dragged 20 Shia Muslim travellers off a bus and killed them at point blank range in northern Pakistan.
"Pakistan's government cannot play the role of unconcerned bystander as the Shia across Pakistan are slaughtered," Adams said.