The police said more than 1000 armed rebels staged the attack late on Saturday on Khalanga, district headquarters of Jumla district, with rebels and security forces clashing for at least six hours.

A senior police officer said the rebels bombed the airport and several buildings, badly damaging a police post, a development office and a land revenue office.

Jail break

"The rebels also broke into jail to rescue five prisoners, while they kidnapped six policemen," he said.

The raid came as Maoists kept up a blockade of capital Kathmandu. They have now vowed to expand their blockade to the Tibetan border.

The government, meanwhile, has appealed to the rebels to call off the blockade and resume negotiations to end the insurgency that has claimed 10,000 lives.

Although the rebels have not physically surrounded Kathmandu, they have warned transporters not to enter the city, leading to a siege mentality that has sent prices soaring in local markets.

Seeking to abolish the country's monarchy, the Maoists have been fighting government forces in a violent insurgency since 1996.