Sri Lankan President Chandrika Kumaratunga has declared a state of emergency in Sri Lanka amid a growing political crisis.
The military has been given wide-ranging emergency powers
The move comes a day after she sacked three ministers, suspended parliament and sent troops on to the streets.
The president has accused the government of making too many concessions to Tamil Tiger rebels.
But she says a ceasefire agreement with the rebels - which ended 20 years of civil war - is not in jeopardy.
Details of the new emergency powers have not been released, but previous emergencies gave the authorities tight control over the media and extensive powers of search and arrest, particularly directed at the minority Tamil community.
Troops have been patrolling the streets and security has been heightened.
The BBC's Anna Horsbrugh-Porter, in the Sri Lankan capital Colombo, reports that most of the country is still in a state of shock over Tuesday's events.
With Prime Minister Ranil Wickramasinghe out of the country and due to meet US President George W Bush in Washington on Wednesday, she says President Kumaratunga appears to be acting quickly while the government is without its leader.
The prime minister, speaking in Washington, has accused the president of bringing Sri Lanka to the verge of "chaos and anarchy".
A cabinet spokesman said that although parliament had been suspended, the government was not in
danger of losing its majority in the legislature.
"The government of Ranil Wickremesinghe continues to enjoy
the confidence of the vast majority of members of parliament," he said. "We are firmly in control of parliament."
He added that a state of emergency had to be endorsed by parliament within 14 days. However, parliament has been suspended by Mrs Kumaratunga.
Peace talks 'to go ahead'
The state of emergency was imposed almost immediately after a news conference held by President Kumaratunga's chief adviser, Lakshman Kadirgamar.
Mr Kadirgamar said the president had suspended parliament and sacked the information, defence and interior ministers because of the worsening security situation in the country.
The move was not linked to the Tamil Tiger proposals for power-sharing, which were made public four days ago.
"The president has specifically asked me to state that the ceasefire agreement stands, and will stand and there is no question about it," said Mr Kadirgamar.
"The president has no intention of resuming or provoking the resumption of hostilities."
The ceasefire between the government and rebels was brokered by Norwegian mediators and signed in February 2002.
The Sri Lankan Government's chief peace negotiator said it would go ahead with direct talks with the Tamil Tigers despite the political crisis.
G L Peiris said arrangements were being made for a preliminary round of talks with the rebels later this month or early next month.
"There are no changes in our plans and we are going ahead to arrange that preliminary meeting," he told reporters.
The Tamil Tigers have dropped a demand for independence in favour of regional autonomy.
But President Kumaratunga's Sri Lanka Freedom Party, which is the parliamentary opposition, had expressed concern about their proposals for a self-governing authority in the north-east of the country.
Sri Lankan Foreign Minister Tyronne Fernando told the BBC that Mrs Kumaratunga had misjudged the security situation.
"It appears that the president unfortunately has acted in great haste right at the time when the peace process is gaining momentum," he said.
The United States has warned that the political crisis could damage moves to end the civil war.
A State Department spokesman said Washington firmly supported the Sri Lankan Government's peace efforts, and urged the president and the prime minister to work together.
The European Union has also warned that the sackings could endanger progress in the peace process.
India has expressed "surprise" at the "sudden political developments" in its southern neighbour.
"We hope that the situation does not provoke a constitutional crisis which would impact on the political stability in Sri Lanka and on the ongoing peace process," said a Foreign Ministry spokesman in Delhi.