A series of explosions rocked a southern Nepalese city on Wednesday where the nation's main political parties planned to hold a mass election rally, officials said.

One man on a bicycle was injured by a blast in the main market of Birgunj, about 100 miles south of Katmandu, said the chief government administrator in the area, Bhola Siwakoti. He was hospitalized in stable condition.

No one was injured in several other minor explosions aimed at disrupting the rally, Siwakoti said.

Three suspects were arrested, he said, adding that security had been stepped up in the area.

"We have policemen guarding every corner of the city and all the entry points," he said.

Senior leaders of the seven-party ruling alliance were to address the rally later Wednesday.

Several ethnic rights groups earlier called a general strike in the area to try to disrupt the rally and were suspected of involvement in the explosions, Siwakoti said.

The groups are demanding greater autonomy in southern Nepal, more seats in the national legislature and a guaranteed number of representatives in the administration.

Since early last year, minority groups have been organizing strikes, transportation shutdowns and demonstrations in the south to demand greater recognition of their rights. Some of the protests have turned violent, leaving at least 80 people dead.

Many southerners say their region has been neglected in favor of the more populated north.

The government announced earlier this month that an election to create a Constituent Assembly to map the country's political future will be held April 10. The election is a key part of Nepal's peace process, in which communist rebels gave up a decade-long armed revolt.

The assembly is to rewrite the constitution and determine the Himalayan nation's future political system.

More than 13,000 people were killed in the decade-long communist insurgency.