Intelligence suggested a threat against the International Monetary Fund (IMF) and World Bank (WB) in Washington and the New York Stock Exchange (NYSE), Department of Homeland Security chief Tom Ridge told a news conference.

He specifically mentioned concern about the Prudential building in New Jersey and the Citigroup buildings in New York City, as well as the NYSE.

"The president made the final decision today, agreeing with the recommendation of (Homeland Security) Secretary Ridge to go ahead and raise the threat level," White House spokeswoman Erin Healy said.

She said the change came after US authorities received new intelligence within the past 72 hours, adding that Bush had been briefed on the situation every day since Friday.

The IMF said it had already been alerted about the threat. "We have been advised by the US authorities of this possible threat and are taking all necessary precautions," said IMF spokesman Bill Murray.

Top federal and local law enforcement officials met in New York during the weekend to discuss new intelligence about a possible al-Qaeda attack against major corporations or high-profile buildings in Manhattan, a police source said on Sunday.

The New York Police Department (NYPD) source told Reuters that increased intelligence 'chatter' from overseas of a possible fresh attack of the city prompted meetings late Friday and early Saturday between NYPD chief Raymond Kelly and Pasquale Damuro, head of the FBI's office here.

New York was the city most affected by the Sept 11, 2001 attacks with almost 2,800 people killed when hijacked planes destroyed the twin towers of the World Trade Center. The city has remained on a heightened alert since then and federal officials have said that the Republican National Convention at the end of August would make an attractive terrorist target.

The threat was first reported by ABC News, which said the authorities were particularly disturbed that the information indicated attacks may be carried out by one or more suicide truck bombings.

Following the meetings, the NYPD issued a statement that said, "Intelligence reporting indicates that al-Qaeda continues to target for attack commercial and financial institutions, as well as international organisations, inside the United States."

The police department said it "recommends that corporate and institutional security directors review their protection of HVAC (heating, ventilation and air conditioning) systems, parking installations, and security in general."

ABC News said sources at several law enforcement agencies told it "that an 'overseas source' provided the information about the threat to New York and that it is more significant than the usual 'chatter' intercepted from likely terrorists that has prompted warnings in the past." ABC said the sources also told it Wall Street firms may be among those targeted.