Sri Lanka's defeated presidential candidate Sarath Fonseka beaten during arrest

His wife was later forced to give a statement to police investigators, who raided her home at midnight, and was questioned until 2am this morning.

The general is believed to have been arrested in relation to an alleged coup plot against Presidential Mahinda Rajapaksa, but a military statement issued last night said he had been taken into "military custody" in connection with "certain fraudulent acts and other military offences committed by him."

A military spokesman said "military investigations" were continuing and that a detailed statement will be issued later. He is expected to face a court martial trial.

Opposition leaders have denounced General Fonseka's arrest as a "brutal, armed kidnapping" in which he and other opposition leaders were physically assaulted by an army major-general.

"There was no decorum. To call it an arrest gives dignity and legality to what was a brutal abduction. He was beaten, dragged along the floor and bundled into a van," said his presidential campaign spokesman, Mangala Samaraweera.

He had been meeting Sri Lankan Muslim Congress leader Rauf Hakim and Mano Ganesan, the leader of the Democratic People's Front, at their Colombo campaign headquarters, when Major-General Sumith Manawadu stormed in with a group of military policemen and ordered them to arrest the general and his aide Senaka da Silva.

He had been planning their forthcoming general election campaign for the parliament, which is expected to be dissolved later today, when troops surrounded his headquarters at around 9 pm last night.