The murders of two alleged rape victims in separate incidents in the north Indian state of Uttar Pradesh over the weekend have sparked demands by women's rights activists for the government to put in place a formal witness protection programme.

On Sunday, an 18-year-old woman, who was due to testify in court in October against a man who allegedly raped her in 2011, was shot dead by four assailants on motorbikes in Mau district.

The previous day, a woman aged 22 - who had accused a man of rape in 2013 - was shot dead as she rode on the back of her husband's bicycle in Sitapur district.

Both victims' families claim the women were being harassed and pressured to withdraw their complaints by the accused, who were out of custody on bail. Police said they are investigating the murders.