Two people were killed during the protests when police tried to prevent a crowd trying to attack a police station.
Among those voicing anger was the cricket star and politician Imran Khan who tweeted: 'The condemnable & horrific rape & murder of little Zainab exposes once again how vulnerable our children are in our society. He said it could not be ruled out that the murders involved a serial killer.
Preliminary examination of the minor's body - that was recovered from a garbage dump on Tuesday - had revealed that she'd been raped before she was killed. He also called for punishment for those police officials who killed protesters in their firing. "For the last two years, we are living in fear, parents are scared to send their kids outside", Zainab's father, Muhammad Amin Ansari, told reporters this week.
Four people have been caught in connection with the previous 11 cases and several suspects are now in police custody, he said, adding that their identities can not yet be revealed.
The police chief said, "By keeping trust of local people and claimants, full cooperation should be acquired and investigation team of police should be briefed completely for diligent performance".
"We will not bury her until we get justice", he asserted at the time. "How was our child kidnapped from a busy market?" he asked. He added that police are waiting for forensic evidence to be collected and analysed. Before this, local police never investigated this element despite a series of child murders.More news: Mudslide-stricken California town is all but emptied out
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This is the 12th such case in the same 2-kilometer area, the regional police office confirmed.
In a speech to thousands of mourners, he blamed the Punjab chief minister, Shahbaz Sharif, for failing to "protect lives and honour of innocent girls" in the province. Protests and demonstrations filled the streets of Pakistan with people demanding justice for the girl. They also threw traffic out of gear by burning tyres on Ferozepur Road and chanted slogans against police and local parliamentarians for their alleged apathy.
"All institutions must work together, and implementation of laws must be strengthened", he said.
Zainab was taken from near her home in Kasur on January 4 while her parents were in Saudi Arabia on a pilgrimage, CNN's Pakistani affiliate Geo News reported.
Laws for the protection of children must be made in line with global laws, he said.