The US Federal Bureau of Investigation (FBI) has warned that the al-Qaeda may be plotting to attack US cities by using helicopters or limousines loaded with explosives, media reports said Monday.

In two nationwide intelligence bulletins, the FBI said terrorists could attempt to hijack commercial, charter or tourist helicopter flights and use them in suicide attacks against buildings, parades or sporting events.

Limousines could be especially useful to terrorists because they were larger than regular cars and might draw less suspicion than trucks, the FBI said.

The warnings were sent Friday night by the FBI and the HomelandSecurity Department to state and local law enforcement agencies, other government officials and private groups, the reports said.

The FBI said however that it had no credible, specific evidenceabout the method, timing or location of any possible al-Qaeda attacks inside the United States.

A report in The New York Times said on Monday that Pakistan hasgiven US officials "credible and specific" information indicating that al-Qaeda has considered using tourist helicopters in terror attacks in New York City.

US Homeland Security Secretary Tom Ridge raised the terrorist threat level for some financial centers in Washington, New York City and northern New Jersey early this month, saying that intelligence from "multiple reporting streams" was "alarming in both the amount and specificity of the information."

Source: Xinhua