ISLAMABAD -- Human Rights Watch said Monday that Pakistan's corrupt and ill-equipped police system encouraged serious rights violations, including arbitrary arrests, torture and "encounter killings," in which police stage shootouts to kill individuals in custody.

In a 102-page report based on dozens of interviews, the New York-based rights group accuses Pakistani police of beating some detainees with batons and leather straps and crushing their legs with metal rods. It says police also use sexual violence and prolonged sleep deprivation. Refugees, the poor and religious minorities are at particular risk, it said.

"Pakistan faces grave security challenges that can be best handled by a rights respecting, accountable police force," said Brad Adams, the rights group's Asia director. "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."

The report is based on interviews with 30 police officers of various ranks, as well as 50 interviews with victims and, their families, and witnesses to such abuse, the group said.

The group quoted an unnamed senior police official as saying that security forces stage mock shootouts to kill "habitual offenders and criminals." Others cited in the report defended the practice, saying it was the only way to bring culprits to justice in a corrupt system.

The report cited the case of Arif Hameed, who was arrested in Lahore in early 2015 along with his brother and sister-in-law, who were later released. The next day police informed the family that he had been killed while trying to escape from police custody, his sister Sameen told Human Rights Watch.

She said the body had four wounds in its chest from bullets fired at close range, indicating he was not on the run when he was shot.

"We know they killed him in a fake encounter," the report quoted her as saying. Her family decided not to pursue a case against the police. "We're weak people with no money or access to influence," she said.

Nayab Haider, a spokesman for police in Punjab province, where Lahore is the capital, denied that extra-judicial killings and death in detention were widespread, saying any such abuses were carried out by individuals and punished by authorities.

Associated Press writer Zaheer Babar in Lahore, Pakistan contributed to this report.