British citizens are being advised by the Foreign Office to leave Iraq immediately because of the stand-off with Saddam Hussein.
Weapons inspectors are continuing their work in Iraq
In new advice issued on Wednesday, the Foreign Office points to "increasing regional tension and the risk of terrorist action" and suggests Britons could be used as human shields by Iraq.
In separate advice, British citizens are also being told to leave neighbouring Kuwait unless their presence there is essential.
And they are advised also to avoid non-essential travel to Israel and the Occupied Territories.
Anybody in the West Bank and Gaza should leave the area, says the Foreign Office.
Families of staff at the British embassy in Kuwait have also been ordered to leave.
Staff who want to depart are also being allowed to do so, the Foreign Office said.
The same is happening for non-essential embassy staff and their families in Israel.
The latest advice is set to add to speculation about possible war.
Thousands of American and British troops are in Kuwait, which would be likely to form a key base for an invasion of Iraq.
The Foreign Office has long advised against travel to Iraq.
Now it says: "If you are considering going to Iraq you should be aware that British nationals were used as hostages during the 1990/1 crisis by the Iraqi regime, being held where their safety was at most risk.
"You should also be aware that there is no British diplomatic presence in Iraq to offer consular assistance."
The advice over Israel signals Foreign Office concern that tensions may rise across the Middle East as the Iraq crisis continues.
It says: "If already in Israel, you should maintain a high level of vigilance and consider whether your presence and that of your dependants is essential.
"This advice also applies to East Jerusalem. You should consider your arrangements for leaving, and in particular check that your travel documents are in order.
"You should register at the embassy or the consulate general.
"In the case of the West Bank and Gaza, we would advise you to leave now while exit routes remain open."
Liberal Democrat foreign affairs spokesman Michael Moore questioned the real reasons behind the travel advice.
He said the safety of British citizens had to be paramount but asked about the timing.
"What has changed to make the need for departure so immediate?" he said.
"Is this advice based on a specific terrorist threat or is this part of the broader build-up to war in the Gulf?"
"If the government's advice is to leave these territories immediately, they also have an obligation to answer these questions immediately."
Earlier on Wednesday, Downing Street declined to be drawn on reports that the UK was working behind the scenes to persuade the US to allow three more weeks for diplomacy.
Tony Blair appeared optimistic on Tuesday that a second United Nations Security Council resolution authorising military action could be agreed.
That comes despite the doubts of countries like France, Russia and Germany about possible war.
Graham Hawkins, from the British School of Kuwait, told BBC News 24 that many of the 3,500-4,000 Britons in the country would stay despite the new advice.
"There is a feeling that something will inevitably happen in the not too distant future but also... that it is unlikely directly to affect us here," said Mr Hawkins.
Have you been affected by this story?
I am currently working in Kuwait and I feel that although Mr Hawkins has made a valid point that there will be a number of people staying here it has not been made clear that some of us feel pressurised into staying by our employers. Mr Hawkins works at a school that is allowing staff to leave and not lose residency, gratuity and wages but there are other institutions here that have made it clear that they expect staff, even those with children, to stay - by leaving staff could lose all benefits and indeed their jobs. As a parent myself with a young child it is hard for me to make a decision knowing that I may not have a job to come back to let alone a visa to get back into the country to find other work and join my husband.
Too cold in England, I am staying in Kuwait.
The simple answer is that if the Foreign Office advises British citizens to leave, then it is the duty of every Briton to heed that warning. War with Iraq looks increasingly likely and at a time of war it is every citizen's duty to back the country. That includes not jeopardising our troops lives by becoming human shields for the enemy. The hundred or so UK Passport holders who feel it necessary to jump in front of a bullet for a tyrannical dictator are tantamount to Lord Haw Haw in the 1940s.
Keith Folkerd, UK
Leave now! The Intelligence Services of our respective nations have information that they cannot share openly as that would give away the means at which the intelligence was gathered (placing the sources at risk). Our leaders cannot say any more as we are about to enter a war, and therefore they use "politic-speak" to hopefully get their "points" across to those who understand. Leave now!
Robert Bruce Campbell, Texas, USA
This advice to British residents in the middle east, clearly shows that behind the scene Bush and Blair will invade Iraq with a total disregard for the UN. Everywhere the British and the American people will be hated, in South Korea the Americans are leaving frightened of a back-lash from the mMslim community, if we really want world peace then we must get rid of these war mongers and have dialogue
Englishman in Korea
Are people mad? It is quite possible that more British people are murdered in the UK in one month than have been murdered/killed by terrorists etc. in all the Arabian Gulf States in the past 20 years. Isn't it time the British Government and public alike put the situation in its true perspective.
Michael Arora, Bahrain
The authorities might me concerned about the lives of the Britons and the tourists in Cyprus. My question is; why nobody at all giving us, the Cypriots, even a little warning or advice if there might a possible war in Cyprus as we all know there is a massive British force is based on our island. Thanks.
Emre Ozgen, Northern Cyprus
Feeling in Kuwait is that something will happen with Iraq but impact minimal in Kuwait.
If the British Government is advising British Citizens to leave Iraq in fear of their safety due to the impending attack on Iraq by the Bush, Howard and Blair troika then it is morally bound to also provide safe passage for Iraqi citizens to a third safe zone.
Trevor Edmond, Australia
Probably I am not alone in being irritated by the British Embassy's advice that Brits should leave Kuwait. My four children attend English schools here and if, as the US and British governments state, there is no immediate likelihood of war, then why should we leave the country? Most of us have our houses in the UK rented out and do not have places in schools in the UK. Where then are we expected to go and what are we expected to do. I agree with the liberal democrat, Michael Moore, that we Britons deserve a much better explanation for the changes in travel advice than we have been given.
Brit expat in Kuwait
How about the situation in Korea? Every time I visit the embassy in Seoul, I'm told only to 'Keep an eye on your email.' There are a good no. of UK and other English-speaking nationals here as teachers of English. Those considering coming to Korea must really be wondering whether to come would be putting themselves at risk or not, never mind those already here wondering whether to stay or break contract and go home. Thankfully, I'm at the end of a two-year contact and am about to leave.
Martin Jones, S Korea (ex-UK)
It is hard to know how much of this is unneccesary scare-mongering on behalf of the Western media! As a teacher, I have a duty to my students and employers. I feel as safe here as I would do in London. And with the excessive build-up of military forces, we must be the best protected country in the world at the minute!
Frances Lennon, Kuwait
I think the Foreign Office has not given out enough information concerning other areas around the Middle East. What about Cyprus? A massive British force is based there, it would be crucial if the war was to commence due to the radar bases which are dotted around the country. What are British residents and tourists suppose to do?
David Meller, England