A Pakistan couple have been arrested for allegedly murdering their seven-year-old maid after she was blamed for letting a pet bird escape, police said, the latest case of violence against child domestic workers in the country.

The couple employed Zohra Bibi at their home in a middle-class suburb of Rawalpindi, near the capital Islamabad, to care for their son of a similar same age.

Police said the girl was "subjected to torture" after she was accused by the couple of freeing one of four pet parrots.

Some 8.5 million people - including many children - are employed as domestic workers in Pakistan, according to the International Labour Organization.

Theoretically it is illegal to employ anyone under the age of 15, but it remains common practice.

Zohra was taken to hospital by the couple on Sunday, but died the following day. The incident was reported to the police by staff at the hospital.

The young girl's body was handed over to her parents, who live in Muzaffargarh, near the city of Multan, more than 500km away from where she was working.

Human rights minister Shireen Mazari confirmed the arrests in a tweet and said the ministry was in touch with police. 

"Violence and physical torture against children will not be tolerated and all those involved in such incidents will be dealt with," the city's police chief added.

Domestic workers frequently face exploitation, violence and sexual abuse, with Pakistan's patriarchal and rigid social-class structure leaving them without a voice.

Children are particularly vulnerable, and Zohra's case is the latest in a growing number of incidents involving minors.

In December 2018, the rising number of abuse cases led the provincial legislature in Punjab to set regulations for the employment of domestic workers, which theoretically grants them rights such as sick leave and holidays.