Kathmandu - At least three people, including a police officer, were killed as violence erupted in southern Nepal during a general strike by an ethnic group, official said Friday.

Local administration in Chitwan district, about 120 kilometres south of Kathmandu, said it had imposed a curfew to contain spiralling violence in several parts of the district.

The violence came on the fifth day of a general strike by the Tharu community across the southern Nepalese plains, known as the Terai.

"Protestors attacked a police patrol during curfew on Friday with knives and machetes and sticks, killing one and injuring one more officer," said Lok Bahadur Chettri, the chief government administrator of Chitwan district.

"Police had to fire in self-defence in several areas, and at least two protestors were killed in the police action," Chettri said. "The administration has clamped down an indefinite curfew to try to contain the situation."

At least 20 people were reported injured during clashes across the district.

The Tharu community has been protesting the government's decision to classify them with the Madhesi ethnic group, a dominant group in southern Nepal. The move deprived the Tharu of greater quotas in government jobs.

They have also accused the Maoist-led government of trying to destroy their identity despite using the Tharu to come to power by promising them greater autonomy.

Protestors have blocked traffic and imposed shutdowns in more than a dozen districts in southern Nepal.

Thousands of people travelling along a major highway have been stranded by the strike.

Nepal's Maoists, who came to power after winning elections in April, have been struggling to end ethnic tensions in southern and eastern Nepal.

More than 250 people have been killed in continuing violence in the Terai in the past two years.

During their decadelong insurgency, the Maoists enlisted the support of ethnic groups across the country, promising them their own autonomous states and a greater say in the country's politics when the Maoists took power. (dpa)