Indian police have launched a manhunt for men suspected of raping and killing three sisters, aged five to 11, in the latest case of sexual violence to grip the country.

The sisters' bodies were found in a village well in Bhandara district in Maharashtra state on Feb. 14 after they had gone missing from school, police officer Javed Ahmed said. The area is more than 1,000 kilometres south of New Delhi, the capital.

As the victims' mother accused police of a shoddy investigation, enraged villagers forced shops to close, burned tires and blocked a national highway passing through the area for several hours on Wednesday, demanding justice.

"The police did not take the case seriously and did nothing for two days," the CNN-IBN television news channel quoted the mother as saying. Her name was withheld.

'Very heinous assault'

One police officer has been suspended for not acting promptly, Indian Heavy Industries Minister Praful Patel, who represents Bhandara district in Parliament, told reporters in New Delhi.

"It is unacceptable. All of us have to hang our heads in shame," Patel said.

Cabinet minister Manish Tewari called the killings a "very, very heinous assault" and announced that Prime Minister Manmohan Singh was sending $18,300 Cdn to the family. The central government has asked state investigators to keep them informed of the investigation.

The fatal gang rape of a young woman in a moving bus in New Delhi on Dec. 16 set off nationwide protests about India's treatment of women and spurred the government to hurry through a new package of laws to protect them.

The gang rape victim and her male friend, who also was badly beaten up in the attack, were dumped naked on the roadside, and the woman died from her injuries two weeks later in a Singapore hospital. Five men are being tried on rape and murder charges in that case.

A new law enacted by the government has increased the sentences for rape from the existing seven to 10 years to a maximum of 20 years. It also provides for the death penalty in extreme cases of rape that result in death or leave the victim in a coma. It has also made voyeurism, stalking, acid attacks and the trafficking of women punishable under criminal law.