Former Sri Lankan military chief Sarath Fonseka, during a media briefing in Colombo on Jan. 29, three days after he lost the presidential election to incumbent Mahinda Rajapaksa. (Eranga Jayawardena/Associated Press)

Sri Lanka's defeated presidential candidate was arrested Monday and will face a court martial, accused of planning to overthrow the government when he was head of the army.

Sarath Fonseka, who as the top general helped defeat the Tamil Tiger rebels, was hauled away from his office by military police after objecting to his arrest, said opposition politician Rauff Hakeem.

Fonseka and President Mahinda Rajapaksa were once strong allies and partners in ending the country's 25-year civil war last May. But they subsequently fell out, and Fonseka quit his post.

They contested a bitter election last month for the presidency. Rajapaksa won by 17 percentage points, according to official results.

As those votes were counted on Jan. 26, hundreds of government troops surrounded a Colombo hotel where Fonseka and other opposition leaders had gathered to await the results. He was later allowed to leave the building, but the show of force foreshadowed Monday's arrest.

Officials have repeatedly accused Fonseka of plotting to kill Rajapaksa and overthrow the government with the help of army deserters and former military officers. Fonseka has called the allegations fabricated and vowed to push on with his political career.

Government minister Keheliya Rambukwella said Fonseka will be tried in a military court on charges of conspiring against the president and planning a coup while army chief.

Mano Ganeshan, an opposition legislator, said Fonseka was "arrested and forcibly carried away" while having a discussion with a group of political allies.

Hakeem said Fonseka objected to being arrested by military police instead of civilian officers, since he was no longer in the military.

The officers dragged Fonseka and his secretary by their hands and legs into their vehicles, Hakeem said.

"He was humiliated and disgraced in the way he was handled. We were just flabbergasted," he said.