KATHMANDU -- Nepalese police have filed charges against 21 Maoists including the rebel's elusive leader over the January assassination of the chief of the kingdom's Armed Police Force, court officials said Tuesday.

District police filed the case Monday at a court in Patan on Kathmandu's outskirts, charging that the 21 Maoists masterminded the killing of Krishna Mohan Shrestha, the highest-level official assassinated since the insurgency began in 1996.

The police asked for life imprisonment for 18 senior Maoists including the rebels' top leader Pushpa Kamal Dahal -- known by the alias Prachanda (The Fierce) -- and Baburam Bhattarai, the Maoist negotiator in failed peace talks this year.

Under Nepalese law, a life term requires at least 20 years in prison. The kingdom does not have the death penalty, AFP reported.

Police called for 10 years in prison each for three lesser-ranking Maoists, Krishna Hari Sainju, Seeta Karanjit and Kamal Bista.

Shrestha, his wife Regmi and his bodyguard Surya Regmi were gunned down January 26 as they went on a morning walk in Lalitpur on Kathmandu's outskirts. The Maoists claimed responsibility for the killings. The assassination sent shockwaves through Nepal's political circles and three days later the government reached a cease-fire with the Maoists.

But three rounds of peace talks failed to yield a breakthrough and the rebels ended the ceasefire on August 27 after the government refused to convene a special assembly to redraft the constitution.

Prachanda rarely makes public appearances and Bhattarai, who moved openly in Kathmandu during the truce, went back underground before the Maoists withdrew from the peace process.

Since the breakdown of the truce, the government has declared the Maoists a terrorist organization, which would allow security forces to arrest rebel leaders. The terrorist label was lifted as a goodwill gesture during the cease-fire.

Other prominent Maoists charged over Shrestha's killing include Krishna Bahadur Mahara and Ram Bahadur Thapa.

The Armed Police Force was created under Shrestha's leadership to combat the Maoists after the rebels broke an earlier truce in November 2001 with a flurry of attacks on often ill-prepared local police.

The Maoists' seven-year insurgency aimed at overthrowing the monarchy has claimed more than 7,900 lives, according to government figures.

Officials have reported 138 deaths since the breakdown of the latest truce.