Kathmandu - A crude bomb injured one person in the Nepalese capital Kathmandu Monday, the police said.

The blast occurred in an area where Prime Minister Girija Prasad Koirala's Nepali Congress Party was scheduled to hold an election rally.

"Unknown assailants hurled the improvised explosive device at a busy public square in Baneshwor area of the city," the police office said. "The device was poorly made and caused little damage."

Witnesses told Nepalese media that they saw unidentified men on motorcycle hurl the bomb and speed away.

No group has yet claimed responsibility for the attack.

It was the fifth such blast in Kathmandu since Friday.

Monday was the last day for electioneering ahead of Thursday's vote and all the parties were holding final campaign rallies.

The election will choose a constituent assembly to write the country's new constitution and ratify the parliament's decision to abolish the monarchy.

Several extremist groups opposed to scrapping the monarchy, and others favouring greater autonomy for ethnic groups, have warned they will disrupt the elections.

In late March, at least two people were killed during an attack on a mosque in south-eastern Nepal. (dpa)