Washington ? Intelligence information suggests al-Qaida attacks may occur as early as this week in both the United States and on the Arabian peninsula, CIA Director George J. Tenet told Congress on Tuesday.

The information led to last week’s raising of the national terror alert level to “orange,” the second-highest level of five. The information came from “multiple sources with strong al-Qaida ties,” Tenet said without providing details.

“The intelligence is not idle chatter on the part of terrorists and their associates,” Tenet said. “It is the most specific we have seen, and it is consistent with both our knowledge of al-Qaida’s doctrine and our knowledge of plots this network — and particularly its senior leadership — has been working on for years.”

The information pointing to imminent attacks was gathered both in the United States and overseas, said FBI Director Robert S. Mueller III, who joined Tenet and other intelligence chiefs to brief the Senate Intelligence Committee in an annual public session on threats to national security.

The CIA director said the information suggests the attack may involve a “dirty bomb” — a weapon that spreads radioactive material over a wide area — or chemical or poison weapons. Officials last week worried the attack was timed to coincide with the Hajj, a Muslim holy period this week.

But Mueller and Tenet said the U.S. government has no specific information pointing conclusively to where, when, or how terrorists would strike. They said raising the national alert level — and taking security measures at government and business centers — makes it more difficult for the terrorists to carry out an attack.

The FBI suspects there are “several hundred” Muslim extremists in this country who focus mainly on fund raising, recruitment and training, Mueller said. But he said the greatest threat to Americans at home are “al-Qaida cells in the United States that we have not identified.”

Tenet and Vice Adm. Lowell E. Jacoby, director of the Defense Intelligence Agency, also raised the dangers of renewed nuclear weapons efforts in North Korea.

“Kim Jong Il’s attempts this year to parlay the North’s nuclear weapons program into political leverage suggest he is trying to negotiate a fundamentally different relationship with Washington, one that implicitly tolerates the North’s nuclear weapons program,” Tenet said.