The government issued the alert saying it had credible information that protests by the Maoists could take a violent turn.

"The security agencies have been asked to remain ready to deal with possible security threats," Home Minister Bhim Rawal said.

Government spokesman and Communication Minister Shanker Pokharel said the army would be mobilized if the Maoists violate the 2006 Comprehensive Peace Agreement by engaging in violence.

From early Wednesday morning, thousands of Maoist supporters marched toward administration offices in Kathmandu shouting slogans such as "Down with military supremacy" and "Prime minister resign."

On Monday the Maoists seized the Metropolitan Office, which staffers have been still unable to enter.

Local television reports said Maoist supporters have also shut down administration offices in all other districts outside the Kathmandu Valley. But there is no report of violence so far.

Meanwhile, at the request of a dozen diplomats who met Maoist leader Prachanda on Tuesday, the Maoists have agreed to suspend their plan to shut down the country's only international airport next Tuesday.

Nepal's Maoists resumed their protests against President Ram Baran Yadav on Sunday, after suspending the protests for a month from mid- September due to national festivals.

The Maoists have been protesting since May, when their leader Prachanda resigned as prime minister after his order to sack the army chief was countermanded by the president.

While their protests were initially directed at pressing the ruling parties to agree to debate the president's step in the parliament, they are now also demanding that a new national unity government be formed under their leadership.

Prachanda led a coalition government for nine months after his party was elected as the largest in a special assembly last year. The assembly is tasked with writing a new constitution.

Nepal's Maoists fought a violent 10-year war with state forces until 2006 when they suspended armed action and signed a peace deal.