Sri Lanka's defeated opposition presidential candidate General Sarath Fonseka was arrested by the army on Monday night, and will be court martialled for military offences committed while he was in service, a fortnight after he suffered defeat at the hands of incumbent Mahinda Rajapaksa.

59-year-old Fonseka, the former Army Chief credited with the annihilation of the LTTE, was arrested along with his media secretary Senaka de Silva while on work at their office in Colombo. Defence Spokesman Major General Prasad Samarasinghe said that Fonseka was taken into custody by the Army and will "face court martial proceedings for military offences committed during his service."

The arrest comes in the wake of reports that Fonseka could face a military court on charges of conspiring to overthrow the government and plotting to kill Rajapaksa. A fortnight earlier, Fonseka - a retired four-star general who served the Sri Lankan Army for nearly four decades - suffered defeat at the hands of Rajapaksa in the high-stakes presidential elections.

Opposition leaders said the army men "forcibly took away General Fonseka while he was having a discussion with three other senior opposition leaders. Fonseka's office was cordoned off by heavily armed troops who blocked reporters and photographers from entering the building and taking pictures.

An aide of the former Army Chief said that "Fonseka and de Silva were told in clear terms to cooperate with the military police". "I heard one of the officers telling Fonseka that he is being charged for criminal conspiracy," he said.

Sunday Times newspaper had yesterday said that the Rajapaksa-led government, which alleged soon after the presidential poll verdict that the former military chief had plotted to kill the President, has consulted its top legal counsel on trying Fonseka in a fast-track court martial.

Earlier this month, Rajapakse sacked a dozen senior military officers whom the defence ministry said were a "direct threat" to national security. Hours before his arrest, Fonseka had assured the family members of former armymen, who were either sacked or arrested by the government, that he will stand behind them during troubled times.