Sept. 11 (Bloomberg) -- The al-Qaeda terrorist network may be planning attacks more devastating than those of Sept. 11, 2001, possibly involving chemical or biological agents, the U.S. government said in a worldwide advisory to its citizens.

``With the second anniversary of the Sept. 11, 2001, attacks upon us, we are seeing increasing indications that al-Qaeda is preparing to strike U.S. interests abroad,'' the government said in an e-mailed statement released through the U.S. Consulate in Hong Kong. ``The U.S. government remains deeply concerned about the security of U.S. citizens overseas,'' it said.

Noting recent terrorist incidents in Saudi Arabia, Morocco and Indonesia, the government said it is concerned European or Eurasian locations may be venues for the next round of attacks. The United Nations said in a report in June attacks in Morocco and Saudi Arabia showed al-Qaeda still posed a threat to international security.

``We expect al-Qaeda will strive for new attacks that will be more devastating than the Sept. 11 attack, possibly involving non- conventional weapons such as chemical or biological agents,'' the government statement said. ``We also cannot rule out the potential for al-Qaeda to attempt a second catastrophic attack within the United States.''

The Qatar-based al-Jazeera television network broadcast a tape yesterday, which included video of al-Qaeda leader Osama bin Laden and his deputy Ayman al-Zawahri walking in mountains.

In an accompanying audiotape, the two men warned of more terrorist attacks against the U.S. The intelligence agencies in the U.S. are assessing the authenticity of the tapes, a U.S. official said yesterday.

The U.S. State Department said in July the war in Iraq has heightened the threat of terrorism to U.S. citizens worldwide, including the possibility of hijackings, suicide attacks and kidnappings.

The latest statement repeats earlier warnings that terrorist actions may include suicide operations, hijackings, bombings or kidnappings. They may also involve commercial aircraft, it says.

Last Updated: September 11, 2003 03:09 EDT