The announcement was made after negotiations between rebels and senior army commanders at the former rebel base of Preah Vihear, near Cambodia's northern border with Thailand.

The BBC's Caroline Gluck: "The top three leaders and up to a thousand loyalists still remain at large"

However, the top remaining leaders of the Khmer Rouge, including Ta Mok, Khieu Samphan and Nuon Chea, are still at large.

The government says it wants to see them brought before a criminal court.

The announcement of the surrenders was broadcast on Cambodian television.

Under a deal negotiated on Friday, around 500 Khmer Rouge fighters will be assimilated into the Cambodian army, along with their lower-level field commanders.

Journalist Nate Thayer: "It does not necessarily mean stability for Cambodia"

An American journalist, Nate Thayer, who has close contacts with the Khmer Rouge, told the BBC the deal would affect several thousand guerrillas and about 30,000 civilian followers.

Our correspondent in Phnom Penh says the Khmer Rouge, which has been held responsible for killing nearly 2 million people during its rule from 1975-1979, has been disintegrating as an effective fighting force over the past two years.

For months, guerrillas have been wandering the jungles of north-west Cambodia in an increasingly demoralised state.

Call for trial

According to one of the defectors, Khem Nuon, the rebels' chief-of-staff, they were joining the government because they had stopped believing the deception of the movement's top three leaders who, he said, should now face trial before an international court.

The rebels said their decision to defect was taken after the country's two main political parties had agreed to form a new coalition government.

The BBC's Caroline Gluck: "Big boost for new coalition government"

The rebels pledged allegiance to the government and said they would now take their orders from senior armed forces commanders.

Cambodia's deputy chief-of-staff, Meas Sophea, said the announcement marked the end of the Khmer Rouge.

However, some analysts say that up to 1,000 men still remain loyal to the Khmer Rouge hardliners, although the threat posed by the rebel group was now minimal.

Our correspondent says the news means that Cambodia is now more unified as a country than at any time in its recent past.