At least four demonstrators have been killed since Saturday in southern Nepal, during protests against the new constitution.
All were shot during clashes with police, in which dozens more protesters and police were also injured.
The protesters, from the Madhesi ethnic minority, say the constitution discriminates against their community.
They have been blockading the Indian border for two months, causing shortages of food and medicine.
Nepal says India is making it worse by tacitly supporting the Madhesi, who have close ethnic ties to north India.
Three of the protesters were shot in clashes with police on Saturday night, while the fourth was shot during clashes in the town of Rajbiraj on Sunday afternoon, says Phanindra Dahal of the BBC's Nepali service.
Dr Prakash Bhattarai, at B P Koirala hospital in the town of Dharan, said all four had died of bullet wounds before reaching hospital.
The hospital says it is also treating 10 other injured protestors, two of whom are in critical condition.
The police say more than two dozen of its personnel were also injured in one of the weekend's clashes. Local ambulances were also attacked.
Along with the shortages caused by the blockade, schools are also reported to have been shut for extended periods across a wide area as a result.