WASHINGTON - The Bush administration raised the nation's terrorist alert level yesterday to "high risk," from "elevated risk," warning that al-Qaida might be planning to attack apartment buildings, hotels and other sites that are not tightly guarded.
In announcing the increase in the alert to the second-highest level, Attorney General John Ashcroft said that "specific intelligence," corroborated by multiple sources, points to a greater likelihood of a terrorist attack on American targets at home or abroad. As a result, the government will tighten security at sites that are seen as high-risk.
But as with previous such announcements, Ashcroft offered no details about specific potential targets or about exactly what Americans should do to protect themselves.
At a news conference with Homeland Security Secretary Tom Ridge and FBI Director Robert S. Mueller III, the attorney general said al-Qaida might plan an attack to coincide with the annual Muslim hajj pilgrimage to the holy city of Mecca. The five-day hajj begins today.
Possible targets that are perceived as "soft, or lightly guarded," such as hotel or apartment buildings, could be especially vulnerable, the officials said at the news conference.
They said terrorists might also try to hit financial targets or other symbols of American power, as they did Sept. 11, 2001. Attacks, the officials said, could involve chemical, biological or radiological explosives, as well as conventional devices.
"Today's change in the threat condition designation from elevated risk to high risk will trigger a series of security precautions," Ashcroft said. "The United States government has specific intelligence and experience demonstrating that heightened awareness on our part deters terrorism."
White House officials said the increase in the alert status was approved by President Bush on the recommendations of Ashcroft and Ridge, as well as of Mueller and George J. Tenet, director of the CIA.
The administration's decision was announced by Ashcroft, but Ridge will have authority to make such announcements after March 1 under the law that established the Homeland Security Department.
The move represented the second time that the threat level has been raised to "high," or "orange" in the government's color-coded scale; the first, which occurred in the period surrounding the Sept. 11 anniversary last year, lasted about two weeks. Elevated risk is denoted by the color yellow, and red denotes the top category, severe, when government facilities would be closed.
In the months after the Sept. 11 attacks, before the color-coded system was established, the administration had twice put the nation on a "high" alert.
After yesterday's news conference, the FBI announced that it was looking for a man from Pakistan who uses the name Mohammed Sher Mohammad Khan and who is thought to have entered the United States illegally after Sept. 1, 2001. Officials believe he might still be in the United States.
A law enforcement official said that uncertainty about Khan's whereabouts was one of numerous factors that led to the elevated alert status. But the FBI said it had no information that Khan is a terrorist.
Ashcroft disputed any notion that the growing confrontation with Iraq was the main factor in the increased alert status.
Ridge said that authorities are not recommending that events be canceled or that Americans' travel plans be changed. People should go about their daily activities, he said, but should "remain aware and remain alert."
Even so, Ridge suggested that people prepare for emergencies. He said, for example, that family members should arrange to be able to contact each other in the aftermath of an attack.
Among the items that will now receive closer scrutiny, Ridge said, will be airport baggage, travel documents and vehicles at U.S. borders. He contacted private-sector industry groups and governors across the country yesterday to warn them of the change.
Maryland Gov. Robert L. Ehrlich Jr. raised the state's threat alert system to match that of the nation, saying that because of the alert, the state would fully staff a 24-hour communications center in a "secure facility" in an undisclosed location.
Authorities from various state agencies, including the state police and the Maryland Emergency Management Agency, are working at the site, where they are keeping in close contact with county law enforcement and emergency services, the governor said.
"People need to use their common sense, and when they see suspicious activity, be aware of it," Ehrlich said. "We have an obligation to be part of homeland security. That is everyone's duty. We don't see the war. There's no standing army. We have no model in our history."
Some local and state law enforcement agencies around the country have complained over the past year that they are already on a high state of alert and that it is unclear to them what changing the threat level specifically requires them to do.
Yesterday, Ridge said his new department would offer those agencies more information, though he gave no examples of action they should now take.
In Baltimore, the city raised its alert status to its second-highest of four.
At an afternoon news conference, Police Commissioner Kevin P. Clark said the city raised its status to be consistent with the nation's. The commissioner said there were no plans to deploy officers to specific potential targets in Baltimore, such as hotels or convention areas. Nor were officers' scheduled leaves canceled.
"It's really no different," Clark said. "We're just really going to have a higher level of awareness. Everything is just normal. Everything is just routine."
Since Sept. 11, the city has twice raised its alert status to the second-highest; the last time was on Independence Day. Citizens who spot suspicious activity that might be related to terrorism are asked to call the city's toll-free Intelligence Hotline at 1-888-223-0033.
Sun staff writers Sarah Koenig, Kimberly A.C. Wilson and David Nitkin and the Associated Press contributed to this article.