A post mortem had revealed that the children were killed about a month and a half ago, senior superintendent of police, G Nageshwar Rao, told the BBC.

Forensic scientists were still trying to establish whether or not the children were sexually abused, he said.

The discovery of the bodies comes amid shock over the grisly killings of 17 young women and children near Delhi.

Smell

The Punjab children - three boys and a girl all under the age of 13 - were reported missing in November.

This mill belonged to me but since a very long time it has been locked - I have offered all possible help

Politician Jagmeet Singh Brar

Their corpses were found on Tuesday night after a foul smell led police to an abandoned rice mill in Muktsar district.

The hands and legs of the victims had been tied and there were burn marks on their bodies, leading police to suspect that someone had tried to dispose of their corpses.

Police have registered a case of murder and attempting to destroy evidence.

The bodies were so badly decomposed that the children's parents, who are all migrant workers, identified them by their clothing.

The rice mill is owned by a senior politician of Punjab's governing Congress party, Jagmeet Singh Brar, but police say there is no evidence to link the politician with the case.

Speaking in Delhi, Mr Brar said he had asked police to investigate the deaths thoroughly. He said he had not visited the rice mill for the past five years and was doing all he could to assist the authorities.

Grief

The Punjab discovery came just 10 days after the remains of 17 young women and children were fished out from a drain in Noida, a suburb of Delhi.

The killings in Noida have caused immense anger

A local businessman and his servant have been arrested and are being held on suspicion of multiple abduction, rape and murder.

The crime has shocked the country and caused immense grief and public anger in Noida, especially against the police.

Furious residents say officers failed to act over the abductions because many of those reported missing came from impoverished families.

The residents say that as many as 40 children have disappeared in the area over the past two years.