Four people were killed and dozens wounded in Monday's clashes between police and protesters from Nepal's southern plains who say they have been sidelined by the peace deal that brought former Maoist rebels into the political mainstream.

The latest violence in the town of Lahan, 125km southeast of the capital Kathmandu, was the worst since the November peace deal that ended a decade of killings, abductions and disappearances that left 13,000 people dead.

The government held an emergency meeting on Tuesday and called for talks with political groups involved in the conflict, including the Madhesi People's Rights Forum that had organised the protests.

The forum says the peace deal offers little for people living in the Terai, which is the bread basket of impoverished Nepal.

"We want a federal structure of government and regional autonomy for Terai ... We want elimination of discriminations against the people of Terai including racial, lingual, cultural and economic," the group's president Upendra Yadav told Reuters.

The Terai region, home to nearly half of Nepal's 26 million people, is a narrow strip of fertile flat land. Its Madhesi inhabitants share closer cultural links with neighbouring India than with Nepalis in the Himalayan mountains of the north.