WASHINGTON -- The FBI urged police nationwide yesterday to step up patrols and watch for signs of terrorist activity during the Fourth of July weekend. Still, officials said there was no specific, credible intelligence indicating an attack was likely.
''We know the US homeland remains a top Al Qaeda target," the FBI said in its weekly bulletin to 18,000 state and local law enforcement agencies.
A constant stream of intelligence indicates that Al Qaeda is determined to stage another major attack this summer or fall, possibly timed to one of a series of symbolic events in the United States and overseas, most notably the political conventions, general election, and Olympics, but also the Fourth of July.
The FBI said police should increase patrols this holiday weekend, vary the timing, size, and routes of the patrols, and make sure all vehicles illegally parked in key areas are approached and their drivers questioned.
The Homeland Security Department had no plans to raise the nation's color-coded terror alert level above its current status of yellow, or elevated. Last week, the agency sent a bulletin urging tighter security to state and local officials and those that operate power and chemical plants and key transportation facilities.
The government's approach to this major US holiday was muted in comparison to Memorial Day, when the FBI and Attorney General John D. Ashcroft issued high-profile warnings that terrorists were nearly ready to strike. In Florida this week, Ashcroft repeated his contention that Al Qaeda was between 75 percent and 90 percent ready to attack again.
FBI Director Robert S. Mueller III said yesterday in Seattle that local, state, and federal officials must cooperate to prevent a new terrorist attack. ''We try to use our imagination to determine where the next threat might come from," Mueller said.
The FBI bulletin cited recent intelligence that continues to show Al Qaeda interest in attacking a range of facilities, including gas stations and refineries; financial and government institutions; civil aviation; nuclear plants and dams; and subways and freight trains.
In Massachusetts, officials at the State Police and the Boston Police Department yesterday would only speak generally about security measures for the holiday.
''We're well aware of the FBI warnings," said Trooper Tom Ryan, a spokesman for Massachusetts State Police. ''The State Police will certainly be at a heightened state of awareness."
A Boston police spokeswoman said the department is monitoring information from the FBI, but she said security plans will differ little from previous years.
''We're doing what we do every Fourth of July," said Beverly Ford of Boston police. ''We have extra officers on the street."
Around the country, state and local officials echoed the federal government's approach to the Fourth.
''We're encouraging New Yorkers to enjoy the holiday but to remain vigilant and aware of their surroundings," said Lynn Rasic, spokeswoman for Governor George Pataki of New York. ''Security will be strong and noticeable at public events across the state."
In Washington, police were setting up 19 security checkpoints along the National Mall for people to enter to watch Sunday's nationally televised fireworks show.
David Abel of the Globe staff contributed to this report.