The soldiers, who were seconded to the United Nations as part of the military observers' force that is supervising a peace deal in the country, were seized in the Occra Hills, 30 miles outside Freetown. The incident is a severe setback for Sierra Leone's new and fragile peace process, which Britain is supporting.
The Foreign Office and the UN force, Unomsil, would not immediately release the names of the soldiers, who are being held with 10 civilians - seven UN officials and three Sierra Leonean journalists - and 18 other international military personnel.
Among those initially abducted yesterday afternoon were an Italian bishop, a UN information officer and three other uniformed military observers, two of them British. They were released in the evening and sent back to Freetown with a message stating their grievances. Bishop George Biguzzi said: "Our mission to the Occra Hills was to observe the handover of 400 children and young women whom we were to bring to Freetown to feed and reunite with their families.
"As we arrived it was clear that something was amiss. The rebels were angry and demanding food and medicine. Very soon there was chaos and panic. Many children ran into the bush and only about 40 children and young women were able to reach the truck taking them to Freetown. We were all led away at gunpoint.''
The Roman Catholic bishop, who has lived in Sierra Leone for 25 years and oversees missions in the north of the country, said: "The rebels' message was that they are from the Armed Force Revolutionary Council [AFRC] and that they want greater recognition than they received in the peace accord.''
A ceasefire has been in force in the small diamond-rich country since a peace agreement was reached in the Togo capital, Lome, on 7 July between the government of Sierra Leone, Nigerian-led peacekeepers and the main rebel group, the Revolutionary United Front (RUF), led by Foday Sankoh.
The AFRC and other fighting groups in the nine-year conflict were mentioned in the agreement and given the same controversial amnesty as the RUF, but were not given cabinet posts or recognised as future political parties.
The rebels, who control three-quarters of the country, have been condemned by Amnesty International and Human Rights Watch for committing some of the world's worst atrocities of recent times. Barbarities inflicted on the civilian population - especially during the last seven months of the campaign to overthrow the elected government of President Ahmed Tejan Kabbah - include dismemberment and mutilation with machetes, and gang- rapes of girls and women.
On 27 July in London, at an international meeting called by Britain, the former colonial power, large amounts of money and personnel were pledged by the Foreign Office and the World Bank for the implementation of the Lome deal.
Britain, which is at the forefront of promoting the peace accord - controversial for its amnesty and the forced cohabitation it envisages between President Kabbah and men who have gained power by such brutal means - is spending pounds 4.5m on "retraining'' rebels to create a new Sierra Leone army, which it will arm. But many see the programme as tantamount to improving the skills of members of future rebel groups or of a new junta.
The AFRC is reported to have a force of between 7,000 and 10,000 men in the Occra Hills. The played a key role in the RUF's advance on Freetown in January, which was narrowly held at bay by the Nigerian-led Ecomog forces defending the government of President Kabbah.
The rebels are deeply divided and it is unlikely that Mr Sankoh, who is at odds with his military chief, Sam Bockarie, can ever return to Freetown to take up his political duties under the Lome peace deal. Mr Sankoh, who remains in Lome, told The Independent by satellite phone that he could not return "for security reasons''.