Kathmandu  - Police shot and killed two demonstrators Saturday in south-western Nepal as members of the Tharu ethnic group defied a curfew and attacked officers and vehicles, government officials said.

The fresh violence came on the 13th day of a general strike by the Tharu across the southern plains known as the Terai.

The clash occurred in Dang district, about 420 kilometres south-west of Kathmandu, when protestors attacked dozens of passenger buses being escorted by police.

Local authorities had imposed a curfew to transport thousands of people who have been stranded during the two-week strike.

"Police fired on the demonstrators who attacked the officers and the passenger buses, defying a curfew, only in self-defence," government administrator of the district Rishiram Dhakal said. "Two protestors were killed and three others injured in the police action."

At least eight police officers were also injured when protestors pelted the police with stones, Dhakal said. The authorities extended the curfew indefinitely after the incident.

The latest deaths brought the total number of people killed during the general strike to five.

Last week, two protestors were shot dead by police in Chitwan district, south of Kathmandu, which in turn prompted protestors to attack a police patrol, killing one officer.

Members of the Tharu community are protesting a recent government decision to classify them with the dominant Madhesi ethnic community in the southern plains. Thauru leaders accused the government of "trying to wipe out their identity" and vowed to continue the strike until the government reverses the classification.

Removing them from the list would give the Thauru a better chance to get government jobs, including in the security forces.

The southern plains have seen violence and protests since the Maoists gave up fighting and joined mainstream politics nearly three years ago.

The region has as many as two dozen armed rebel groups demanding greater autonomy and right to self-determination.

More than 250 people have been killed in the unrest in southern Nepal over the past two years. (dpa)