No one was injured in the blasts in Pokhara, in central Nepal, or the western towns of Butwal and Bhairahawa shortly after the rebels' unilateral ceasefire ended at midnight on Monday.

In its first official reaction to the end of the truce, Nepal's royalist government said it stood ready to protect the country.

"It is unfortunate. The state is prepared for any eventuality," junior Information Minister Shris Shumsher Rana told Reuters. "We are ever vigilant."

The explosions raised fears of a major resumption of violence across the troubled Himalayan kingdom if the rebels step up their attacks.

The Maoists first declared a three-month truce in September, but later extended it for another month under popular pressure.

The United Nations said yesterday it was "deeply concerned" that Maoist rebels in Nepal have ended their unilateral ceasefire, warning that the troubled Himalayan kingdom now faces an escalation of violence.

"The United Nations in Nepal is deeply concerned that the people of Nepal are again faced with the prospect of an escalation in fighting, the loss of more lives, and increased and prolonged suffering," it said in a statement.

In the past two months, it added, UN Secretary General Kofi Annan had repeatedly urged the rebels to extend their ceasefire and the Nepalese government to reciprocate the truce.

"The United Nations regrets that the many appeals from the people of Nepal and the international community have not been heeded and no progress appears to have been made towards a peaceful resolution of the conflict," it said.

On Monday, Prachanda, the elusive rebel leader, said the ceasefire would not be prolonged further and accused government troops of provoking his forces to break it.

The loyalist government of King Gyanendra, who fired a previous government and seized power in February, had refused to respect the truce, saying the Maoists could not be trusted.

As the ceasefire ended, local media reported that the rebels, who have a strong presence across much of the countryside, were planning to attack the heavily defended capital, Kathmandu.

Commentators and ordinary Nepalese called for talks to try to end the fighting that has raged for a decade. More than 12,500 people have died in the rebel insurgency that aims to topple the monarchy and establish one-party communist rule.

The violence has delayed parliamentary and local elections and wrecked the economy of the aid-dependent nation.

"The government must take the initiative for talks between the king, political parties and the Maoists," said Nepal Samachar-patra, a local newspaper.

Sunita Chamling, a housewife in Kathmandu, said the government should have matched the Maoist truce.

"Peace had a chance under the ceasefire. Therefore, the government should have responded to the Maoists," she said.

Security has been stepped up across the mountainous country.

"Soldiers are patrolling the streets and there is fear in the minds of people," journalist J. Pandey said from Nepalgunj, the biggest town in west Nepal where the Maoists have a strong presence.

King Gyanendra has called for elections to 58 municipal councils to be held on Feb 8. But the Maoists have pledged to derail the polls and the seven main political parties, pressing the king to restore democracy, have announced a boycott.