US officials warned Asia today to be on guard against terror attacks in crowded sea lanes and in financial centres such as Hong Kong.
Speaking in Singapore, a State Department official said Washington had good reason to believe terror groups would target economically critical shipping lanes such as the Malacca and Singapore Straits.
"We have begun to focus on the potential of a disastrous maritime terrorist incident," Mr Matthew Daley, deputy assistant secretary of state, told a security conference.
The United States had raised its fears with Asian governments for the past year but remained concerned about the safety of the region's shipping arteries, Mr Daley said.
Assaults by al-Qaeda on commercial shipping in Yemen and the Arabian Sea and planned attacks in several straits, including the Strait of Gibraltar linking Spain and North Africa, showed that US concerns were not simply theoretical.
In Hong Kong, FBI director Robert Mueller said the city and commercial centres like it could be targets for al-Qaeda and other terror groups seeking to inflict economic damage.
The US warnings coincided with a threat by an unknown group to attack Asia-Pacific countries that have backed the war on terror begun by Washington in response to the September 11th, 2002, attacks on the United States.
South Korea's embassy in Bangkok had received a threatening letter, a Thai police general said; Pakistan's envoy to Thailand said his embassy had received a similar letter.