A bomb exploded Monday in a busy market area in a southern Nepal town where a political rally was being held, killing at least four people and wounding 14 others, police said.

Police said the explosion occurred in Janakpur during rush hour. People had gathered in the area for a political rally to demand a separate state in a new constitution being drafted by the country's Constituent Assembly.

Witnesses said the bomb was hidden in a red motorcycle parked next to the rally, police said.

Police detained one person for questioning. A little-known group calling itself Janatantrik Terai Mukti Morcha claimed responsibility for the bombing.

The town is about 200 kilometers (125 miles) southeast of the capital, Katmandu.