KATHMANDU, Nepal (AP) — Hundreds of security forces patrolled a west Nepal area Tuesday where ethnic protesters, demanding statehood, attacked police with spears and knives a day earlier leaving at least six officers and three protesters dead and many others injured.

A curfew was imposed and policemen and soldiers were rushed to Tikapur, 400 kilometers (250 miles) west of Kathmandu, where the clashes happened Monday.

Government administrator Raj Kumar Shrestha said authorities were in control of the town and surrounding areas and there were no protests or reports of curfew violations.

At least 20 policemen were being treated in hospitals after being hurt in the clashes.

It was not clear if other protesters were also killed as many fled into the jungle and nearby villages after the troops were called into the town.

Local news reports said the death toll could be as high as 20.

Home Minister Bam Dev Gautam told the Constituent Assembly, the national parliament, that the protesters surrounded police who were enforcing a curfew and attacked them with stones, knives and spears.

Police and soldiers from neighboring districts were rushed to the town, Gautam said.

The protesters from the Tharu ethnic group are demanding a separate state in the new constitution, which is being finalized in the Constituent Assembly. They say a separate state would give them a stronger say in local affairs. They have organized strikes and street demonstrations, but the protests turned violent Monday.

Nepal has been governed by an interim constitution for years. A Constituent Assembly elected in 2008 failed to draft a new charter in four years because of major disagreements among political parties, and a second assembly was elected in 2013.

But there has been pressure on the politicians to speed up the drafting process since an earthquake in April killed thousands of people.

The main political parties now agree there should be seven federal states, but smaller political parties and ethnic groups oppose either the number or makeup of the states.

New York-based Human Rights Watch called on the government to order an independent investigation into the deaths and said the security forces must respect basic rights.

"The violence ... and the deployment of the army threatens to further increase tensions in an already charged situation," the statement quoted Brad Adams, the group's Asia director, as saying.