A four-year-old girl was raped before being strangled to death in northwest Pakistan, a district mayor and doctors have said.

The body of the victim, who is being named as Asma, was found in a sugarcane field on Sunday in the Jandarpar Gujjar Garhi district of Mardan city, a day after she went missing.

"I have seen the autopsy report of Asma and it clearly says that she was raped before being strangled to death," district mayor Himayatullah Mayar told Al Jazeera on Wednesday.

"She comes from a very poor family, her father is a labour worker in Saudi Arabia. Asma was just playing outside of her house when she was kidnapped."

Doctors also told local media that the child had been raped.

Police confirmed that the child died of asphyxiation and were investigating the claim of rape.

"According to the forensic report, the girl was subjected to violence," district police officer Mian Saeed told local media. "However, we cannot confirm if she was raped or not until we get the complete report."

The incident comes as the country reels from the recent rape and murder of seven-year-old Zainab Ansari, a case which ignited widespread protests and stirred uneasy conversations about the sexual abuse of children in a country where the issue is taboo.

Zainab's body was discovered in a heap of rubbish last week in the northeastern city of Kasur. She had disappeared on January 4 after leaving her house to go to a tuition centre.

Protests calling for justice in various parts of Kasur turned violent, resulting in at least two deaths and several injuries.

Local TV footage showed police officers shooting at protesters to disperse crowds.

In 2017, at least 12 similar incidents were reported in the Kasur district alone, local media reported.

In the first half of 2017, more than 1,750 cases of child abuse were reported across Pakistan, according to Sahil, a non-governmental organisation that works on the issue of child sexual abuse and exploitation.

Of the cases in the first six months of last year, 65 percent took place in Pakistan's Punjab province.