The FBI quietly warned its agents nationwide of unconfirmed information from a captured senior Al Qaeda official that terrorists may be planning attacks against supermarkets or shopping centers, law enforcement officials said Wednesday.

The warning, sent Tuesday to all FBI field offices and relayed to some state and local police, cautioned that the information was unsubstantiated and did not include specific information about possible targets, timing, numbers of people involved or any particular method of attack.

The warning said that Al Qaeda operatives inside the United States may be planning attacks against civilian targets, possibly including banks, shopping centers, supermarkets and shops, law enforcement officials said. The information came from Abu Zubaydah, the highest-ranking Al Qaeda terrorist leader in U.S. custody, they said.

The information that prompted the new warning was considered less reliable than last week's about possible attacks on banks in the northeastern United States.

"We're trying to downplay this," said one law enforcement official, speaking on condition of anonymity.

The latest alert, like last week's, did not change the nation's threat status, which remained at "yellow," using the new system of color codes. Yellow represents the midrange. To qualify for the next-highest orange alert, a threat must include a specific time and date and be corroborated and credible.

Unlike last week, the latest warning was issued only to FBI field offices, which quietly relayed the information to local joint-terrorism task forces typically made up of state and local police agencies.

"There is no official alert," a law enforcement official said.

A spokeswoman for Taubman Centers of Bloomfield Hills, Mich., which operates 29 malls in 13 states, said the company did not plan to step up security or make any other changes.

"Nothing has changed since Sept. 11," spokeswoman Karen McDonald said. "We continue to be on a heightened level of alert." She noted that the centers still restrict access in such sensitive areas as loading docks and delivery areas.

Also Wednesday, the State Department alerted Americans abroad that terrorists may be preparing to strike, especially in the Persian Gulf and Arabian Peninsula.

"There is growing concern," the department said in a statement. It cautioned Americans to be careful and said "softer targets" may be selected by terrorists because security at U.S. installations has been strengthened.

Last week, authorities cautioned that they had no information about a specific plot or threats to any specific financial institution. But the FBI warned publicly about possible "physical attacks," based in part on information from Zubaydah, two officials said. But it was unclear if he was telling the truth, and officials said he could be lying in an effort to create a panic.

Abu Zubaydah is alleged to have been one of Usama bin Laden's top planners of terrorist operations, with knowledge of Al Qaeda plots and operational cells. He was captured in Pakistan on March 28 and is recovering from three gunshot wounds he received in the raid.

There have been no reports of any bank closings in response to last week's alert, which remains in effect.