As fears of new terrorist attacks in the US gripped Washington last night, the Bush administration raised the alert status from yellow to orange, the second highest level of risk in a five-colour scale. Conor O'Clery reports from New York.
Earlier the US, Britain and Germany said they were temporarily closing down their embassies and consulates in Saudi Arabia because of "imminent" terror threats there.
The moves follow warnings from Saudi officials and the FBI that the recent bombings in Saudi Arabia and Morocco were a prelude to more attacks by al-Qaeda on Saudi Arabia or the US.
This is the fourth time the threat level has been raised from "significant risk" to "high risk" in the US since the September 11th attacks.
New York is permanently on orange, and will now go on "high orange alert", with increased security at bridges, tunnels and airports.
Police with automatic weapons would be put back on New York streets, and New Jersey and Connecticut will provide hundreds of state troopers to protect commuter trains into Manhattan, the New York state governor, Mr George Pataki, told a press conference in Albany last night.
On Monday, Saudi Arabia's ambassador to Washington, Prince Bandar bin Sultan, said there was "a high level of chatter regionally and in other international spots" about a possible big attack in Saudi Arabia or the US.
Suicide attacks on three foreign compounds in the Saudi capital Riyadh on May 12th killed 34 people, including eight Americans, and wounded almost 200.
US embassy websites warned yesterday that "further terrorist attacks are being planned against unspecified targets in Saudi Arabia", and that the US embassy in Riyadh and consulates in Jiddah and Dhahran will be closed until Sunday.
The British Foreign Office said its embassy in Riyadh, consulate in Jiddah and trade office in Khobar will remain closed until Saturday. A similar statement was issued by the German Foreign Office.
The FBI warned in a bulletin to law enforcement agencies that the recent bombings in Saudi Arabia and Morocco could be a prelude to attacks in the US by a resurgent al-Qaeda.
The message contradicted President Bush's May 4th statement that "al-Qaeda is on the run" and "they're not a problem any more".
The FBI said the bombings in Saudi Arabia indicated that al-Qaeda remained "active and highly capable", and could launch new attacks in the US. "Attacks against US and Western targets overseas are likely; attacks in the United States cannot be ruled out."
The prospect of a new attack on the US has provoked questions about Mr Bush's conduct of the war on terrorism, an issue considered off limits before now.
"We are paying for what we did in Iraq because when you see al-Qaeda come back that is the price we pay for taking our eye off the ball," presidential candidate Mr Howard Dean told a rally of Democratic women in Washington.
The Department of Foreign Affairs last night said there were no plans to close the Irish Embassy in Riyadh. A spokeswoman for the department said officials would continue to monitor the situation.
The department has advised against all non-essential travel to Saudi Arabia.