A statement released Saturday in the name of an Al Qaeda-linked (search) group threatened attacks against Italy if Rome doesn't withdraw troops from Iraq by Aug. 15.

Italy's interior minister said the statement required "maximum attention," but the group cited as making the threat has denied issuing such a warning.

The statement was signed in the name of Abu Hafs al-Masri Brigades (search), the group which claimed responsibility for the March 11 Madrid train bombings (search), and released on an Islamic Web site known as a clearing house for militant-related material.

"Our cells in Rome and other Italian cities are prepared and mobilized to carry out their missions when the ultimatum ends Aug. 15 ... to bring unbearable hell to the lives of the silent people here in Italy," said the message.

The threat appeared similar to one sent Aug. 1 to London-based Arabic newspaper Al-Quds Al-Arabi, which warned Italy to pull its soldiers out of Iraq within 15 days or face "waves of earthquakes."

But on Aug. 3, Abu Hafs al-Masri Brigades posted a statement on its own Web site denying that it had given Italy a 15-day ultimatum. It is unclear who the actual authors of the threatening statements are.

Such claims and counterclaims illustrate the difficulties of determining the authenticity of Web threats or whether those who post them have any ability to carry them out.

However, Italian Interior Minister Giuseppe Pisanu issued a statement saying the latest threat required "maximum attention because, faced with terrorism, no signal of a risk can be neglected or underestimated."

The Abu Hafs al-Masri Brigade takes its name from a top Al Qaeda lieutenant who was killed in a U.S. airstrike in Afghanistan in 2001. It has claimed responsibility for several attacks on Western targets, but counterterrorism experts question if it has any agents capable of launching attacks and say some of its claims are obviously false or exaggerated.