Police in southern Nepal opened fire on ethnic protesters blocking the nation's main highway, killing two in fresh clashes that have also left dozens injured, officials said Sunday.

Police were trying to stop the protesters from blocking the main East-West highway when they were attacked with petrol bombs, spears and bricks around midnight, police official Bhim Dhaka said Sunday.

He said that 25 policemen and several protesters were injured in two separate attacks. A curfew was imposed in the area to stop further violence.

Ethnic Madhesis have been protesting for months the new constitution that established new federal states. They want a bigger area and more seats in parliament.

The protests have shut down most of southern Nepal for weeks and closed a key border crossing with India, causing shortages of fuel, medicines and other supplies.