Sri Lankan President Chandrika Kumaratunga has suspended parliament and sacked three powerful ministers, plunging the country into crisis.
Security forces have been put on high alert
Troops have been ordered to guard key installations, including the state television station.
Prime Minister Ranil Wickramasinghe, her rival, accused the president of seeking "chaos and anarchy".
Mr Wickramasinghe, who has a small majority in parliament, is in the US to brief President Bush on negotiations with the Tamil Tigers.
Mrs Kumaratunga, who has taken control of the ministries, is at odds with the government over the peace process.
She has wide powers to dismiss Mr Wickramasainghe, who defeated her party in December 2001 elections, and call a new poll.
Days ago, Tamil Tiger rebels submitted a power-sharing peace proposal.
Mrs Kumaratunga's Sri Lanka Freedom Party, which is the parliamentary opposition, said in a statement it was concerned about the Tigers' proposals, for a self-governing authority in the north-east of the country.
Tamil Tiger spokesman Daya Master said no comment would be made on the developments in Colombo until full details had been received.
Mr Wickramasinghe said he would be resolute in implementing his mandate and would continue his mission in the US.
He said would not allow Mrs Kumaratunga to "undermine the peace process and economic prosperity".
"The irresponsible and precipitous action of the
president is aimed at plunging the country into chaos and
anarchy," he said in a statement.
Addressing the Sri Lankan people and the security forces, he said: "I call upon all of you ... to remain calm and vigilant in the face of this deliberate attempt to end the peace process."
Military spokesman Colonel Sumedha Perera said "several platoons" of troops had been deployed to the state printing press, TV and radio, and power stations to "prevent any disturbances".
There were reports that hundreds of heavily armed soldiers had surrounded the printing press, where a government gazette is expected to publish news of the dismissals.
Wickramasinghe and Kumaratunga have an uneasy relationship
Police throughout the country have been put on maximum alert and all leave cancelled.
The BBC' Frances Harrison in Colombo says the deployment is fairly routine in a country where security has traditionally been high, but it does seem to indicate some nervousness that this latest move by the president might encounter resistance.
Mrs Kumaratunga said earlier that she had dismissed the information, defence and interior ministers in the "national interest".
"This step has been taken after careful consideration, in order
to prevent further deterioration of the security situation in the
country," she said in a statement, adding that the reasons for this action would be made known in due course.
This measure was followed by the suspension of the parliament until 19 November, a move which analysts say in effect pre-empts any attempt to challenge the sackings.
The suspension means that a reading of the country's budget, which was due to be discusssed on 12 November, will be put on hold.
Mrs Kumaratunga has an uneasy relationship with Mr Wickramasinghe's government, who defeated her party at parliamentary elections in December 2001.
Our correspondent says the sackings seem to have ended any hope of further co-habitation.
Mrs Kumaratunga has been at odds with Defence Minister Tilak Marapuna, Interior Minister John Amaratunga and Information Minister Imthiaz Bakeer Markar over their handling of the peace process.
All three ministers still hold other cabinet-level posts.
The US Government said on Monday it believed it was possible for both sides to reach agreement on the issue of an interim administration.
But Washington has failed to comment on the details of the Tigers' proposal.
The rebels signed a ceasefire with the government in February 2002, bringing to an end two decades of fighting which have left more than 60,000 people dead.
In their latest proposals, the Tigers dropped a demand for independence in favour of regional autonomy.
But opposition politicians say the proposals are in breach of the constitution and the Tamils are using the interim administration to prepare the legal ground for breaking away.
Send us your views on the political crisis in Sri Lanka using the postform below:
Sri Lanka has begun her dramatic collapse in to a bottomless abyss with these new dramatic developments. Under the present government there was a faint glimmer of real hope for peace, but now it seems like a distant dream and to me many Sri Lankan will return to a living nightmare. Sadly this power hungry craze is endemic to all third worlds leaders who want to remain in power for as long as they can while plundering the country for their own gain.
Tina Edward Gunawardhana, UK
This clearly shows how the politicians of the majority of communities handle the ethnic war. When one comes forward the other rejects and vice versa. I appeal to the international community to see the real reason why the Tamils want a self determination. Can Tamils expect reasonable solutions from in this kind of politicians? This is more over justifying the Tamils struggle towards the separate nation. To improve the current situation an international pressure should be used on the President and her party to carry on the peace negotiation.
Rajendran, Sri Lanka
Mrs. Kumaratunga has once again demonstrated her inability to deal with Sri Lanka's political and economic issues in a constructive manner. This irresponsible move on her part, motivated purely by her need for political power, is typical of the leadership her family has provided the country since independence. Selfish political gain rather than a determination to solve problems has characterized their political tenure.
Sharmini Mahendran, USA
It shows how desperate the president is to get back in to power. As far as the security is concerned there is no imminent threat from the LTTE or anyone else. LTTE's proposals on Interim Administration are yet to discussed and agreed. President is prepared to use any measure, how undemocratic it may be, to oust the elected government and no concern whatsoever about the people or the country.
It is a sad day for Sri Lanka. Once again politicians are putting their selfishness before the welfare of the people. The last two years have brought peace and prosperity to ordinary Sri Lankans of all walks of life particularly the poor. They can earn a living and move without standing in long queues to be searched etc. This is a legacy from JR Jayewardene - dividing the power between the Prime Minister and the President. Previously the President was a nominal figure. Who will suffer as a result of this new developments? The poor of course.
I fully back Tamil tiger proposals. They now have given up the separate state solution as the international countries wanted. Now the foreign countries should back Tigers and let the Tamils to run their affairs. The Sri Lankan is incapable of running the country and they are corrupt. The sacking of the minister shows how the Sri Lankan democracy works.
Sanjeevan Siva, UK
A surprising move indeed! I doubt if any commentator would have thought that the Singhalese president would have the audacity to take a decision that so transparently betrays its anti-Tamil agenda. The dark history of Sri Lanka seems to repeat itself, where once again, the well received Tamil steps towards peace, are likely to be side-stepped and overpowered through this crisis.
S Sivaskanthan, Australia
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