At least 25 people were killed today in clashes between former Maoist rebels and supporters of an ethnic Madhesi group, forcing authorities to impose a curfew on a border town, police and officials said.
The violence between the Madhesi People's Rights Forum, which represents an ethnic group living in Nepal's southern plains, and Maoists took place in the town of Gaur, 80 km (50 miles) southeast of Kathmandu.
Government officials said the two sides had opened fire at each other, causing dozens of deaths and injuries.
"The death toll is at least 25 people so far," Kuber Kadayat, a police official, said by phone from Gaur.
The United Nations condemned the violence and said hospital sources indicated some victims had died of head injuries caused by beatings with bamboo sticks. It said dozens of people had been admitted to hospital.
Including today's deaths, the highest toll on a single occasion, at least 56 people have been killed in protests organised by Madhesi activists over the past three months.
The violence has overshadowed a peace process between the government and Maoists to end a decade-long insurgency in which about 13,000 people have died.
The Madhesi group has been demanding more government jobs and more seats in parliament for its people, who live along the narrow strip of the Terai region bordering India, home to nearly half Nepal's 26 million people.