Parliament in Sri Lanka has been dissolved with effect from midnight on Tuesday ahead of new elections, officials said.
The vote for the 225-seat legislature is likely to be held in April, but an official announcement is expected by the Commissioner of Elections in the next few days.
Two weeks ago, President Mahinda Rajapaksa of the ruling United Peoples Freedom Alliance (UPFA) was re-elected for a second term.
The dissolution comes after the arrest of former army commander Sarath Fonseka, who led the military victory over the separatist Tamil rebels before unsuccessfully running in the presidential election.
Fonseka was arrested at his Colombo office on Monday while discussing plans to contest the parliamentary vote, said Somawansa Amarasinghe, head of the opposition Marxist JVP party, who was present at the time of the arrest.
"The military police stormed into the meeting and took him away. He agreed to surrender to the police, but they (the military police) insisted they had power to arrest him took him away," Amarasinghe said.
"From our point of view it is an abduction," he said.
A separate statement said Fonseka was arrested on charges of "committing alleged fraudulent acts and military offences," but did not give details of the offences.
Government defence spokesman Keheliya Rambukwella accused the ex-army chief of leaking information discussed at Security Council meetings, thereby posing a threat to President Rajapaksa's life.
The director general of the Media Centre for National Security, Lakshman Hulugalle, said Fonseka, who ran as the presidential candidate of an opposition coalition, would appear before amilitary court on charges of conspiring against the government.
Hulugalle said Fonseka was arrested for conspiring to topple the government and for creating divisions within the army when he was the commander.
The government had earlier claimed that Fonseka and the opposition planned to assassinate Rajapaksa.
Fonseka was expected to contest the presidential election results in the courts this week.
At least 10 political parties, including three main opposition parties, plan a sit-in against Fonseka's arrest near the Supreme Courts complex in Colombo on Wednesday.
Fonseka commanded the army in its defeat in May of the rebels of the Liberation Tigers of Tamil Eelam, which had been fighting for a separate state for Sri Lanka's Tamil ethnic minority.
He was demoted soon afterward to the ceremonial post of defence chief of staff and decided in November to challenge the president with the backing of three main opposition political parties.
The ex-army chief managed to win 40 percent of the vote against 58 percent for Rajapaksa, according to official data.
Since the elections, more than 20 members of Fonseka's staff, including a retired major general, have been arrested.