Former US president Jimmy Carter said Saturday he was confident Nepal's long-awaited elections next week would proceed peacefully, despite threats of violence from anti-poll protesters.

Carter, 89, is in Kathmandu to lead a 50-person team from the Atlanta-based Carter Center, who will monitor Tuesday's crucial vote, only the second such polls since a 10-year civil war launched by Maoist rebels ended in 2006.

"We have been very pleased at the preparations for the election," he told reporters in the capital.

"We have great confidence... that the people of Nepal will orchestrate a very successful and honest and fair and a peaceful election," he added.

Carter's NGO monitored Nepal's landmark 2008 constituent assembly polls, which ended royal rule and transformed the country into a secular republic.

Since then, political infighting has confounded efforts to draft a constitution and conclude the peace process, leading to the collapse of Nepal's first constituent assembly in May 2012.

Carter said he planned to meet with political leaders and with the chief justice of the supreme court, who is heading Nepal's interim administration, before the November 19 vote.

A hardline faction of the Maoist party that swept the 2008 polls has threatened to disrupt the elections, with anti-poll protesters torching buses and hurling explosives at vehicles this week.

Carter, a 2002 Nobel Peace Prize laureate, met with the hardliners during a visit to Nepal last April and asked them to renounce violence in the run-up to the polls.

The 33-party alliance, headed by the Communist Party of Nepal-Maoist (CPN-M), says elections cannot be carried out under the interim administration and want the polls to be postponed until a cross-party government is put in place.

In a statement late Friday, UN Secretary General Ban Ki-moon urged the hardliners to allow the vote to take place "in an atmosphere free of violence and intimidation".

"The secretary general appeals to all stakeholders to conclude these elections peacefully, and to redouble their efforts in the urgent task of constitution-making", the statement said.

Meanwhile, a prominent Maoist party leader, Ram Karki, along with a Maoist election candidate, Keshav Rai, suffered serious injuries in a bus accident Saturday east of Kathmandu that left a total of 30 people hurt, police told AFP.

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 constituent assembly, which will also serve as a parliament.