New Delhi:  Indian police arrested a doctor couple on Wednesday who allegedly locked up their 13-year-old maid while they went on holiday in a case that has spotlighted abuse of under-age domestic servants.

Police say the affluent couple, both medical doctors with thriving practices, locked the child in their flat in New Delhi last month with little food when they went to Thailand on vacation.

Police deputy commissioner A.K. Ojha said police arrested the couple acting on a "tip-off" after they went into hiding following their return at the end of March.

The girl was rescued by fire fighters after four days when neighbours spotted her crying on the balcony of the apartment in an upmarket block in the east of the capital in a case that has made headline news.

The girl accused her employers, Sanjay and Sumita Verma, of beating her and pulling out her hair. The couple had also allegedly installed closed circuit cameras inside the house to keep a watch on her.

"I was regularly beaten up by the couple and their 11-year-old daughter. They would hit me with a ruler and pull my hair when I made mistakes," she said in a statement to India's Child Welfare Committee.

She also said she was underfed: "I would get only two chappatis (unleavened flat bread) a day."

In 2006, India passed legislation banning employment of children under 14 in households, roadside eateries and hotels, but the law is widely flouted in the country of 1.2 billion people.

Police have filed a case against the couple, accusing them of violating the Child Labour Prohibition act. A lawyer for the couple has denied the allegations of mistreatment and said the child had locked the door from the inside.

Social welfare activists say children are widely employed by India's middle classes, who often claim they are doing good by giving jobs to destitute children.

"This case is the tip of the iceberg," Bhuwan Ribhu, spokesman of Bachpan Bachao Andolan, a non-governmental organisation whose name translates as Save the Childhood Movement.

"This case is unusual, it came to public attention," he told AFP. "But most families they know there is very little chance they will get into trouble - it's greed."

"The real reason is these children are employed is that they are cheap labour, easily dominated and there is no deterrent. Prosecutions are miniscule."

It is common to see shabby, underfed maids employed by well-dressed Indian families in parks and restaurants, looking after children.

The child, from the poverty-stricken eastern state of Jharkhand, had been given by an uncle to a servant agency which placed her with the couple.

India's Child Welfare Committee said the girl had told them she had done all the laundry and cleaning for the family and received no pay.

Last month, a US judge said a maid should be paid nearly $1.5 million for "slavery" for her Indian diplomat employer in New York who forced her to work 15-hour days for $70 a week. India rejected the ruling, citing diplomatic immunity.