Two protesters have died in rioting over the latest in a series of child murders in the Pakistani city of Kasur.
The body of seven-year-old Zainab was found in a rubbish dump on Tuesday, several days after she went missing. She had been raped and strangled.
Angry demonstrators say the authorities are doing little to stem the spate of abductions, sexual assaults and killings.
Police in Kasur say there have been 12 similar murders in the past two years.
They say five of them are linked to one suspect who is being hunted by hundreds of officers and DNA samples have been taken from 90 possible suspects.
The two protesters were killed after police shot at an angry crowd attempting to storm a police headquarters in Kasur, about 20km (12 miles) south of Lahore.
Zainab's murder has sparked outrage across the rest of Pakistan.Well-known film and cricket stars demanded the killer be caught and the military offered support to the police.
Zainab went missing on her way to a Koran recital. Her body was found about 2km from her home.
However, Zainab's family say the police did not take action after they reported her disappearance and it was relatives who recovered CCTV footage of Zainab's movements before she disappeared, not the police.
The footage showing a girl being led by the hand by a man was circulated widely on social media.
"If the police would have acted immediately, the culprit would have been caught," Zainab's father told Geo TV as he arrived back in the capital Islamabad from Saudi Arabia, where he had been on a pilgrimage.
Police say similar incidents appear to be taking place in Kasur every other month.
Last month, a nine-year-old girl went missing in the city centre after going to the shops near her home. She managed to escape her captor and return home but has been left severely traumatised by her ordeal, reports say.
Zainab's murder has led to widespread anger on social media, where the hashtag #JusticeforZainab was one of the top trending topics worldwide.
Actors and cricketers were among those demanding the murderer's arrest.