KATHMANDU (AFP) - Demonstrators protesting next week's election in Nepal torched vehicles and hurled an explosive at a bus in Kathmandu late on Wednesday, injuring eight people, the police said.

A 33-party alliance, headed by the Communist Party of Nepal-Maoist (CPN-M), has urged a vote boycott and imposed a ban on motorised transport until Nov 20.

"The attackers threw a petrol bomb at the bus. Eight passengers who were injured have been rushed to the nearby hospital," Mr Ganesh K. C., a police spokesman, told AFP.

"Protesters also set eight vehicles on fire and vandalised five other vehicles around the country," he said.

Police have arrested more than 130 demonstrators since Monday, he added.

CPN-M says the Nov 19 vote, the country's second national election since a 10-year civil war ended in 2006, is illegal.

They argue that elections cannot be carried out under the interim administration, headed by the chief justice of the supreme court, and have called for polls to be postponed until a cross-party government is put in place.

Protesters linked to the anti-poll alliance have previously disrupted the distribution of election material and set candidates' vehicles on fire.

More than 100 parties, including three major ones - the Unified Marxist-Leninist, the Nepali Congress and the Maoists - are fielding candidates for the 601-seat Parliament, which is also expected to act as a Constitution-drafting body.