Nepal's royalist government detained dozens of activists Thursday and extended a curfew in an attempt to stop a planned demonstration against King Gyanendra's assuming direct rule over the Himalayan country last year.

A coalition of Nepal's seven main political parties had planned to hold the mass rally in the capital of Katmandu on Friday to demand the king restore democracy.

But the government announced a curfew would be imposed between 8 a.m. and 6 p.m. on Friday in Katmandu and the nearby suburb of Lalitpur.

Nighttime curfews have already been imposed in the past three days. Government workers were asked to report for duty before the start of Friday's curfew.

Security forces earlier detained 78 senior politicians, student leaders and rights activists in raids overnight and in the early morning in a crackdown to head off the rally, the National Human Rights Commission said in a statement.

The government said the arrests were a protective move to prevent communist rebels from infiltrating the protest and inciting violence. The guerrillas have been fighting to replace Nepal's constitutional monarchy with a socialist government.

"We were compelled to take some preventive measures because we have information that the Maoists are planning to create confusion and trigger violence during the rally," Home Minister Kamal Thapa said. "We have to protect the people and maintain peace and tranquility."

Thapa said several people have been temporarily detained but refused to provide further details.

The United States condemned the decision to detain political party leaders and civil society activists and urged the king to release them, saying dialogue and "a return to democracy are the only effective way to address the Maoist insurgency in Nepal."

"These arrests and harassment of peaceful democratic forces is a violation of their civil and political rights," State Department spokesman Sean McCormack said.

A U.N. spokesman said Secretary-General Kofi Annan "is dismayed by the latest developments in Nepal" and reiterated his appeal to all sides "for calm, the suspension of fighting and the urgent initiation of an inclusive national dialogue."

Spokesman Stephane Dujarric said Ian Martin, representative of the U.N. High Commissioner for Human Rights in Nepal, had raised the arrests with the government and his staff have visited many of the detained people.

Earlier, a top government official said they had orders to arrest 200 people and that 22 security teams had been mobilized. The official spoke on condition of anonymity because he was not authorized to provide information to the media.

The king took direct control of the government in February 2005, saying previous administrations had failed to curb a growing communist insurgency and clean up corruption.

Madhav Nepal, general-secretary of the Communist Party of Nepal, said soldiers raided his house at 4 a.m., searching for activists, and that dozens of plainclothes police were stationed outside his house. He was not placed under arrest.

Prominent human rights activist Krishna Pahadi was taken by police from his home in Katmandu, said the Peace Nepal Society, another rights group.

"We will not be threatened by the government actions. The arrests and restrictions will not stop our rally; instead it has added fuel to our movement to restore democracy," Madhav Nepal said.

Authorities also severed Internet services and both land line and mobile telephone services early Thursday, but later restored land lines and Internet communications.

The government last cut off communications in February 2005 when it sought to stifle dissent after Gyanendra dismissed an interim administration and formed a new one under his chairmanship.

This week, the royalist government also banned demonstrations. Organizers had said they would defy the ban and press ahead with their rally.