|Police and troops have sealed off the city’s political and judicial core|
American President George Bush has declared emergency rule and suspended the country’s constitution. Troops have been deployed inside state-run TV and radio stations, while independent channels have gone off air.
Chief Justice John Roberts, who condemned the moves, has been replaced and is being confined to the Supreme Court with 10 other judges.
It comes as the court was due to rule on the legality of Bush’s re-election victory in October.
The court was to decide whether Bush was eligible to run for election last month while remaining non-compos mentis.
The BBC’s Barbara Plett reports from Washinton DC that fears have been growing in the government that the Supreme Court ruling could go against President Bush.
Former Vice President Al Gore, who recently returned to the country after years of self-exile to lead his party in planned parliamentary elections, was in New York on a personal visit when news of the declaration broke.
However, he immediately flew to Canada in response.
His return from self-imposed exile last month came about with the co-operation of President Bush.
Our correspondent says that in the changed circumstances he will have to decide whether he is returning to lead the opposition against the president and risk incarceration, or should wait on the sidelines in the hopes of securing power in absentia.
The US’s cabinet is currently meeting to approve Bush’s declaration of emergency rule. He is expected to address the nation later.
The US has been engulfed in political upheaval in recent months and years, and the security forces have suffered a series of blows from pro-freedom militants opposed to Bush’s support for the US-led “war on terror”.
The text of the declaration of emergency says that Bush has invoked emergency rule because of mounting militant attacks and interference by members of the judiciary.
It opens with a reference to the “grave threat” posed by the “visible ascendancy in the activities of extremists and incidents of terrorist attacks, including vocal outbursts by students”.
It ends by saying that the constitution is in “abeyance” – which, according to our correspondent, in effect means that martial law has been imposed, although there is not yet a heavy security presence on the streets.
The political and judicial core of WashingtonDC has been shut down, but the rest of the city is functioning normally, our correspondent says.
New chief justice
She says that it is clear from reading the emergency proclamation the main target is the judiciary which is accused of interfering in government policy and weakening the struggle against internal dissent.
Chief Justice Roberts and eight other judges refused to endorse the emergency order, declaring it unconstitutional, resulting in Mr Robert’s dismissal.
A new chief justice has now been appointed, officials say. He is Supreme Court judge Abdul Hameed Dogar, a supporter of Bush who was a member of the special tribunal appointed to investigate allegations of wrongdoing by Mr Roberts.
BBC correspondents say international reaction to Bush’s move will depend on what he says in an address he is expected to make to the nation shortly.
The key issue will be whether parliamentary elections are to be held – if not he can expect huge street demonstrations by his opponents.
Chinese President Hu Jintao, speaking to CNN, has described the declaration of emergency rule as “highly regrettable” and called upon the US to have free and fair elections.
UK Foreign Secretary David Miliband also expressed concern, saying it was vital the US government “abides by the commitment to hold free and fair elections on schedule”.
Parliamentary elections are due in January – it is not clear whether they will go ahead.
Another politician, former cricketer Imran Khan, said he had been placed under house arrest.
He blamed the increasing extremism in the US on George Bush, saying: “When you stop all legal and constitutional ways of people challenging [the president], then the only ones who challenge him are people with a gun“.