KATHMANDU, Nepal (Reuters) - Nepal's King Gyanendra on Monday ordered the army to crush Maoist guerrillas fighting to topple the monarchy after a surge of violence pushed the Himalayan nation a step closer to civil war.

Gyanendra declared a state of emergency, announced curbs on freedom of movement and expression and gave authorities powers of detention and search, state radio said.

Gyanendra, who became king in June after many other royal family members died in a palace massacre, deployed the army against the rebels on the advice of the government for the first time since Nepal adopted a constitutional monarchy in 1990.

``His majesty the king has authorized the deployment of the army on the recommendation of the National Defense Council,'' state radio said.

The army, which includes the formidable Gurkha troops, is seen as sympathetic to the monarchy and Nepal has until now been reluctant to deploy it against the Maoists for fear of upsetting the kingdom's delicate constitutional balance.

The crackdown followed the worst violence in five years over the weekend as Maoist rebels abandoned a cease-fire and attacked police and army posts across the country. Authorities said more than 100 people had died over the past three days.

The situation was quite grave, said Rabindra Khanal, a political science professor at Tribhuvan University in Kathmandu. ``I think we are entering into a civil war,'' he told Reuters.

Lok Raj Baral, a second professor at Tribhuvan, said such large-scale violence was unprecedented. ``For the first time the state has reacted very strongly,'' he said.

MAOISTS DECLARED 'TERRORIST ORGANIZATION'

State television also reported that the government had declared the Maoists ``a terrorist organization.''

At least 45 people were killed Friday and Saturday in a rash of attacks by rebels on security posts in western Nepal.

Then late Sunday, more than 80 people died, many of them rebels, when hundreds of guerrillas stormed buildings, including an airport control tower and army barracks, in Sallery in eastern Nepal, government officials said.

In New York, U.N. Secretary-General Kofi Annan (news - web sites) was deeply concerned at the flare-up in violence, his spokesman said.

``The secretary-general regrets that the insurgents abandoned peace talks with the government that started last August. He will continue to follow closely the developments in Nepal,'' spokesman Fred Eckhard said.

An Indian foreign ministry spokeswoman said India, which shares an open border with Nepal, also was monitoring events closely. India, which has gone to war with neighboring Pakistan twice over the disputed Himalayan region of Kashmir (news - web sites), accuses Islamabad of using Nepal as a base for anti-India activities, a charge its nuclear rival denies.

Some 2,000 people have died since the revolt to impose a communist republic started in 1996.

The rebels stepped up the violence after the massacre of royals, including King Birendra, by a drunken Crown Prince Dipendra, who also killed himself. Gyanendra, the king's younger brother, then assumed the throne.

The rebels, led by a shadowy leader who calls himself Prachanda -- loosely translated as ``awesome'' -- agreed a truce in July and to hold peace talks after centrist Prime Minister Sher Bahadur Deuba came to power on a pledge to end the revolt.

But after three rounds of talks, the rebels dropped out last week, saying peace moves had been scuttled by the government's rejection of their call for a new constitution.

The constitution permits a declaration of a state of emergency if the nation's sovereignty or integrity is threatened. Parliament would have to approve any state of emergency within three months, and it could stay in force for six months, renewable by parliament for another six months.