KATHMANDU, Nepal - Police opened fire Monday on protesters attempting to disrupt a political rally, killing at least three, in southern Nepal where violent protests last year left dozens dead and blocked the border, causing severe fuel shortages.

Home Ministry official Bal Krishna Panthi said police first tried to disperse the protesters with bamboo batons and tear gas before firing their guns.

He said three people were fatally shot and 33 police officers were injured in the clash. He could not say how many protesters were hurt.

The Communist Party of Nepal (United Marxist Leninist) had attempted to hold a rally in Rajbiraj town, about 400 kilometres southwest of Kathmandu. Ethnic Madhesi groups from south Nepal oppose the party and have vowed not to allow its rallies.

CPN-UML was in power and their leader Khadga Prasad Oli was prime minister when the Madhesis held protests between August 2015 and February 2016. Oli refused Madhesi demands for changes to the country's new constitution that would give the ethnic group much more territory in new federal states.

Madhesi protesters shut down southern Nepal towns for months, blocked the border with India and stopping the supply of fuel and medicines to protest the new constitution.

The protests fizzled out but the group vowed to continue to pressure the government. A new administration that took power in August 2016 promised to address the demands by the Madhesi, but that proposal is still being considered in parliament.

The CPN-UML, the second-largest party in Nepal, has been holding rallies in south Nepal towns since Saturday ahead of district and municipal elections scheduled for May.