The guerrillas threatened officials and candidates contesting the Feb. 8 elections to 58 municipal assemblies and called for a strike to wreck a vote the government says could lead to parliamentary elections in 2007.

The Maoists, fighting to topple the Hindu monarchy in the Himalayan kingdom, have not explained their threat but are known for beating, kidnapping or killing people who disobey them.

"If it includes threats to the life or physical integrity of individuals taking no active part in hostilities, or the taking of hostages, such action would be a grave violation of international human rights standards," said Ian Martin, chief of the Office of the UN High Commissioner for Human Rights in Nepal.

"I must ask for a clear undertaking that no such action will be ordered or encouraged," he said in a statement late on Friday.

Municipal elections have been delayed since 2003 because of the Maoist revolt that has killed more than 12,500 people.

Nepal's seven main parties have also pledged to launch protests to thwart the polls, saying they were aimed at legitimising the regime of King Gyanendra, who seized absolute power on Feb. 1, fired the government, suspended civil liberties and jailed politicians.