The US authorities have discovered a terrorist plot in the advance stages of planning against U.S. facilities in Germany, CNN reported yesterday, quoting a senior federal official.

The official said the plot, which has been planned for some time, included the use of bombs and small arms against U.S. targets -- possibly military facilities, buildings or U.S. citizens.

He called it a "very real threat" and said an al-Qaida affiliate franchise in Europe might be responsible for the plot.

However, a senior Pentagon official said there is "nothing new" beyond what led the U.S. State Department to issue a warden message raising security at American facilities three weeks ago.

A spokesman for the U.S. Embassy in Berlin and a spokesman for the German Interior Ministry also said they're not aware of a new threat beyond what led to that message.

Meanwhile, the Department of Homeland Security issued a statement saying there was no credible intelligence to suggest an imminent threat on U.S. soil.

In a related development, U.S. air marshals are providing additional protection of flights between Germany and the United States, law enforcement officials.

Germany, which will host the G-8 Summit next month, has been engaged in a security crackdown recently.

More than 900 personnel took part in anti-terror raids, arresting more than 40 people.