The UCPN-Maoist Chairman was heading towards Belauri to address a rally ahead of the Constituent Assembly polls on November 19. No one was injured by the blast that occurred in a forested area, said police spokesman Ganesh Khatrichhetri.
Bombs were also found and defused by an army unit near the venue where Prachanda was scheduled to address the closing ceremony of his party's Mechi-Mahakali National Campaign, police said.
The bomb attack came a day after an army bomb disposal team defused an improvised explosive device (IED) planted merely 100 m away from a dais from which Prachanda and former premier Baburam Bhattarai were to address an election rally at Kanchanpur.
The injured were taken to a nearby hospital.
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In another incident, two tourist buses were torched by protesters near Pokhara.
Police rounded up at least a dozen CPN-Maoist activists in Chitwan district of southern Nepal for trying to enforce the nine-day transport strike.
Forty-four activists quit the CPN-Maoist in Jajarkot district to distance themselves from the violence blamed on the party.
A 33-party alliance, headed by the Communist Party of Nepal-Maoist, a breakaway faction of UCPN-M, is boycotting the crucial polls. This is Nepal's second national election since a 10-year civil war ended in 2006.