Police have arrested the main suspect involved in the rape and murder of a seven-year-old girl in the central Punjab province of Pakistan, a police official told Al Jazeera.

Zainab Ansari was found dead in a rubbish dump on January 9 in Kasur, several days after her disappearance.

An autopsy revealed she had been raped and strangled to death.

"The suspect lives in the same [area] where Zainab lived," a police district official confirmed to Al Jazeera on Tuesday.

The suspect has confessed, the official said.

"He was arrested before, but was released as we did not have evidence. After that, he shaved his beard off so that no one could recognise him."

The rape and murder of Zainab Ansari was the 12th such case in Kasur district in the last year, according to local media reports.

The incident led to angry protests in various parts of Kasur that resulted in at least two deaths and several injuries.

In 2015, Kasur was in the international headlines when hundreds of videos of child molestation surfaced, and police later arrested several members of a racket involved in selling child pornography to websites in Europe.

Most of the victims were under 14, including a six-year-old boy, according to officials.

The hashtag #JusticeForZainab has trended on social media in Pakistan and elsewhere.