They are not serious, they are not sincere, they have betrayed Nepal before and we don't trust them anymore

Sher Bahadur Deuba Nepalese prime minister

Describing himself as Nepal's "number one pro-peace person", the prime minister told the BBC that the rebels had broken their word before.

"They are not serious, they are not sincere, they have betrayed Nepal before and we don't trust them anymore," he said.

No talks could be held until the Maoists surrendered their arms and renounced violence, Mr Deuba, who is on a visit to the United States, added.

The government has received broad international support

Correspondents say the Maoists' statement, which was sent to newspapers in the capital, Kathmandu, is probably genuine.

Purporting to come from Maoist leader Prachanda, the statement says the rebels are responding to what it describes as the advice of friends.

It comes a week after the rebels renewed an offer to resume peace talks with the government.

Heavy losses

Some observers detect desperation among the rebels and a decline in their morale - but others argue they are merely buying time to re-organise.

Political parties and human rights organisations have been putting pressure on the Maoists to lay down their arms and resume talks, which they unilaterally abandoned last November.

The rebels warn they will stay vigilant

Unconfirmed reports say the Nepalese army killed hundreds of rebels last week when they mounted an offensive against their strongholds in the west.

The figure is impossible to verify as the media and human rights groups have been barred from the conflict zone.

This week, the Maoists responded with an attack on a security post in the western district of Rolpa, in which scores are reported to have been killed on both sides.

In the statement released to the press, the rebels warned they would respond with a "fierce and decisive battle" if government forces did not respect their truce.

In all, about 4,000 people are thought to have been killed in the six-year-old Maoist revolt which has wrecked Nepal's economy.

The unilateral ceasefire announced by Nepal's Maoists coincides with a similar announcement from their counterparts, the People's War Group (PWG), in the Indian state of Andhra Pradesh.