The attacks could target European or Eurasian locations "possibly to closely coincide with the anniversary of the September 11 attack," said the warning issued through foreign consulates.

"We expect al-Qaeda will strive for new attacks that will be more devastating than the September 11 attack, possibly involving non-conventional weapons such as chemical or biological agents.

"We also cannot rule out the potential for al-Qaeda to attempt a second catastrophic attack within the United States," the statement said.

There could be "suicide operations, hijackings, bombings or kidnappings," added the warning.

Likely targets are facilities where US citizens and other foreigners congregate, "including residential areas, clubs, restaurants, places of worship, schools, hotels, outdoor recreation events or resorts and beaches."

The world paused yesterday to remember the victims of the September 11 attacks, with the spectre of Osama bin Laden returning in a videotape threatening more strikes on Americans.

A memorial ceremony at Ground Zero in New York, where the twin towers of the World Trade Center once stood, was a low-key but emotional affair, as children related to the victims read the names of all those who perished.

US concerns were heightened by the broadcast on Qatar-based Al-Jazeera television Wednesday of footage of bin Laden and right-hand man Ayman al-Zawahri that experts said could spur on new attacks by Islamic militants.

In the tape, bin Laden praised the "loyalty, sincerity, magnanimity and courage" of the suicide hijackers who crashed airliners into the World Trade Center, the Pentagon near Washington and a field in Pennsylvania.

Al-Zawahri also called on Iraqis to "devour" their American occupiers, warning the real battle with the United States has yet to begin.

The September 11 attacks forced a dramatic change in US foreign policy and led to military campaigns in Afghanistan and in Iraq, where the death toll among US troops is mounting as they face almost daily guerilla attacks.

US President George W. Bush warned Americans that his "war on terror" was not yet over and that al-Qaeda was plotting new strikes against the world superpower.

"The memories of September 11 will never leave us. We will not forget the burning towers," Bush said.

"We will not wait for further attacks on innocent Americans. The best way to protect the American people is to stay on the offensive, to stay on the offensive at home and to stay on the offensive overseas."

Bush, who led mourners in New York for the first anniversary, was not at Ground Zero this year and his chosen representative Vice President Dick Cheney also skipped the main ceremony at the request of city officials.

The names of all those who perished were read aloud once again at Ground Zero, but this time by children related to the victims.

The ceremony's participants paused in silence four times -- twice to mark the times that each hijacked plane hit the towers and twice to mark the times that each tower fell.

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