Police say three detained suspects have confessed to the gang rape and slaying of two teenage cousins who were found dead in northern India last week.

The search for two additional suspects continued today for a fourth day.

India has long had a reputation for tolerance for sexual violence, but the gang rape and killing of the 14 and 15-year-old cousins in Uttar Pradesh state caused outrage across the country.

The two cousins went missing from their home in a village in Uttar Pradesh's Budaun district on Tuesday evening when they went out to go to the toilet.

The next morning, villagers found their bodies in a nearby orchard.

Local police said a post-mortem confirmed that the girls, from the Dalit community, had been raped.

Their family had earlier complained that police had refused to help find the missing girls.

Police officer Atul Saxena, said today that police were preparing identity sketches of the two missing suspects, based on descriptions provided by the arrested suspects.

Authorities also have arrested two police officers for failing to investigate when the father of one of the teenagers reported the girls missing.

The poor state of women's safety in India has been under the spotlight since the gang-rape and murder of a 23-year-old student on a moving bus in the capital Delhi in 2012, which led to the introduction of tougher rape laws.