The former rebels clashed with activists of the Nepal Federation of Indigenous Nationalities, who called a general strike in Chitwan district, 200km southwest of Kathmandu.

"Police arrested 12 people following clashes between the Maoists and supporters of the ethnic group. Several people were injured," said top district official Netra Rawal.

Trouble started after the Maoists tried to open a highway that was blocked by the group, which represents minorities from the hills of southern Nepal. The situation was now under control, Rawal said.

The group plans more protests to demand increased government representation and proportional representation in elections due before mid-June.

In Nawalparasi town, 250 kilometres southeast of the capital, two people were arrested after a scuffle between the Maoists and activists of the Mahadeshi Janadhikar (People's Right) Forum, police said.

The ethnic body, whose pro-autonomy protests earlier this year left 29 dead, imposed a one-day general strike in the region demanding the release of dozens of their activists who were kidnapped by the ex-rebels Friday.