Human Rights Watch on Monday accused Pakistan's police of routinely carrying out extra-judicial killings, torture and arbitrary arrests, and called on Islamabad to implement urgent reforms of its under-resourced forces.
The findings were contained in a new report based on interviews with more than 30 police officers and 50 victims or witnesses of abuse across three of the country's four provinces.
In addition to noting habitual rights violations -- including more than 2,000 so-called "encounter" killings in 2015, which are often believed to have been staged -- the report said police often found themselves in thrall to powerful individuals who subvert the law for their own purposes.
"Pakistan faces grave security challenges that can be best handled by a rights-respecting, accountable police force," said Brad Adams, Asia director at Human Rights Watch.
"Instead, law enforcement has been left to a police force filled with disgruntled, corrupt and tired officers who commit abuses with impunity, making Pakistanis less safe, not more."
In the biggest city Karachi, encounter killings have surged since 2013 as paramilitary forces and police have stepped up raids against Taliban militants, criminals and armed political activists.
The term is used to describe staged confrontations in which police or troops kill suspects and later claim they were acting in self-defence.
The report found that those from marginalised groups -– refugees, the poor, religious minorities, and the landless -– are at particular risk of violent police abuse.
It said: "Torture methods include beatings including with batons and leather straps, stretching and crushing legs with metal rods, sexual violence, prolonged sleep deprivation, and mental torture, including witnessing others being tortured.
"Senior officials told Human Rights Watch that physical force is often threatened and used because the police are not trained in professional investigation and forensic analysis methods, and thus resort to unlawfully coercing information and confessions."
Local politicians meanwhile are able to halt investigations against suspects with political connections, and to harass or file charges against opponents.
In addition to being on the frontline of the country's battle against homegrown Islamist terror, Pakistan's police forces contend with high-levels of organised and violent crime -- including kidnappings for ransom and drug trafficking.
A recent wave of high-profile murders of women in the name of family honour have cast a spotlight on blood-money laws which allow the relatives of victims to forgive perpetrators in exchange for money.