Masked gunmen stormed a house and killed nine police cadets in Pakistan's eastern city of Lahore on Thursday, police said, the second attack on security forces claimed by the Taliban in relatively peaceful Punjab province in four days.
The Pakistani Taliban said it was responsible and vowed more violence in the region.
Lahore city police chief Aslam Tareen said three policemen were also wounded.
"At around 6am, masked gunmen on three motorcycles stormed the house and opened fire. The victims were trainees at the Punjab Jail Academy," Tareen said.
Many of the police were from the northwestern Khyber-Pakhtunkhwa province near the border with Afghanistan, a hotbed of Pakistan's insurgency.
Taliban spokesman Ehsanullah Ehsan said the police from that region had been targeted because they treated Taliban detainees poorly.
"We were looking for them for a long time as their attitude with our people in jails is very inhuman and insulting," he said by telephone from an undisclosed location.
The Pakistani Taliban's threat of further attacks raised the prospect of more violence in a region that has been largely spared of insurgent trouble in recent years.
On Monday, gunmen killed six soldiers and a policeman at a riverside military encampment in eastern Pakistan, 100km north of Lahore. The Pakistani Taliban also claimed responsibility for that attack.
In a separate incident in the southwestern Baluchistan province, six coal miners and a doctor were found dead in the Degari area, officials said, about 100 km east of the provincial capital Quetta.
The victims were kidnapped last week from the Marwar coalfield, and had multiple bullet wounds on their bodies.
Much of the violence in Baluchistan, Pakistan's biggest but poorest province, has been blamed on ethnic Baluch separatists, who are fighting a protracted insurgency, demanding more autonomy and control over the natural resources of the province.
Militants loyal to al Qaeda and the Taliban are also active in Baluchistan, which borders Iran and Afghanistan.