Karachi: The rape and murder of a young girl in Pakistan has sparked calls for #JusticeforZainab around the world, amid anger over a spate of unresolved child sex crimes in the conservative nation.

Police recovered the body of Zainab Ansari, aged about 7, on Tuesday from a garbage dumpster in the town of Kasur in eastern Pakistan, four days after she was reported missing.

Pakistani Nobel Prize laureate Malala Yousafzai and cricketer-turned-politician Imran Khan were among the celebrities using the hashtag, which is trending on Twitter. "This has to stop," tweeted a "heartbroken" Yousafzai, an outspoken campaigner for girls' rights in her homeland.

"Authorities must take action."

A 2011 Reuters poll found Pakistan to be the world's third most dangerous country for women, due to acid attacks, child marriage and punishment by stoning. Ansari was the twelfth girl to be abducted, raped and killed in the past year in Kasur district, police said.

"This is not the first time such horrific acts have happened," said Khan. "We have to act swiftly to punish the guilty and ensure that our children are better protected."

Actresses Mahira Khan and Sanam Saeed were among those who demonstrated in Karachi, Pakistan's largest city, on Thursday. "We need to start talking about sexual abuse openly," said Khan, one of Pakistan's most popular actresses.

"We need to include that in our school curriculums. Awareness is key. Associating abuse and rape with shame is why countless (attacks) go unheard of. Reuters