The retired general who sought unsuccessfully to defeat his onetime ally in Sri Lanka's presidential election last month was arrested late yesterday by the military police, raising concern that the country was veering into political vengeance and autocracy after having barely emerged from a quarter-century of war.

Retired general Sarath Fonseka, who lost the election to Mahinda Rajapaksa by 17 percentage points, was taken into custody by dozens of military police officers at his office, where he was meeting with several parliament members to discuss coming legislative elections, said Mano Ganesan, a member of parliament who was present at the meeting.

"They arrested him and carried him out like a dog," Ganesan said in a telephone interview.

Lucien Rajakarunanayake, a government spokesman, said that Fonseka had been arrested under military law for actions during his tenure as the chief of army staff, the last post he held before retiring in November.

"He was arrested by the military," Rajakarunanayake said. "It has nothing to do with the election."

The arrest was not unexpected. Rumours have swirled for weeks about government allegations that Fonseka had plotted to overthrow the government or assassinate Rajapaksa with the help of army deserters loyal to him.