One U.S. government analyst said al Nashiri, in his 30s, a Yemeni born in Saudi Arabia, has been "the directing mind" for al Qaida operations in the Persian Gulf and Red Sea. He has also been active in operations against U.S. targets in Southeast and Southwest Asia, said this official, who asked not to be identified.
According to a former senior CIA official, al Nashiri was also the master plotter of the Oct. 6 bombing of the oil tanker Limburg and the October 2000 suicide attack on the USS Cole that killed 17 American sailors and injured 39 others.
Rohan Gunaratna, author of "Inside Al Qaida," said al Nashiri was involved in a plot two years ago to bomb U.S. embassies in Yemen, Bangladesh and India, foiled when two accomplices were arrested along with 100 pounds of high-explosive.
A longtime U.S. intelligence official, who asked not to be identified, said al Nashiri is believed to have been plotting additional strikes against U.S. warships and other craft transiting the Suez Canal or operating in the Red Sea.
Al Nashiri was "very intent on causing economic damage" not only to the United States but to "Western targets in general," focusing on oil tankers traveling the region, this official said.
Al Nashiri was also involved in plotting against targets in Malaysia, and may have been on a mission when arrested while at an airport en route to Malaysia about 10 days ago, he said.
Al Nashiri is in CIA custody and being interrogated by the CIA at a "secret site in a foreign country." The official refused to elaborate but confirmed that U.S. intelligence specialists are closely examining the hard drive of al Nashiri's computer. Former CIA counter-terrorism chief Vince Cannistraro told United Press International that the interrogation of al Nashiri has already produced a spate of terror alerts against U.S. targets such navy ports, facilities and warships in the region.
Former CIA counter-terrorism official Larry Johnson said Malaysia acted as an alternative planning base for last year's Sept. 11 attacks on the World Trade Center and the Pentagon.
On Wednesday, the State Department specifically mentioned Malaysia as a country where Americans and foreigners could face risk of attack by the Jemaat Islamiyah terror network, whose leaders were trained in Afghanistan by bin Laden.
But al Nashiri's main efforts appear to have been directed at naval targets. In addition to being the plotter and explosive specialist in the USS Cole attack, al Nashiri is alleged to have plotted to sink the USS Sullivans in Aden the same year, and this year was involved in a scheme to sink U.S. and British warships in the Straits of Gibraltar -- a plot broken up in Morocco, U.S. officials said.
He was also involved in an earlier plot to blow up U.S. navy warships in Bahrain, U.S. officials said.
Gunaratna told United Press International that al Nashiri had been trained by bin Laden's master bomber, Abu Khebab, in Afghanistan at the Derunta camp near Jalabad.
According to federal law-enforcement officials, al Nashiri is considered the most senior al Qaida operative to be captured since the arrest of Abu Zubayda, al Qaida's operations chief in Pakistan last March.