WASHINGTON — The names of dozens more people have been added to the government's terrorist watch list and no-fly list after a failed terrorist attack on Christmas prompted U.S. officials to closely scrutinize a large database of suspected terrorists, an intelligence official said today.

People on the watch list get additional checking before they are allowed to enter this country; those on the no-fly list are barred from boarding aircraft in or headed for the United States.

The review of the National Counterterrorism Center's massive Terrorist Identities Datamart Environment (TIDE) database was prompted by the attempt to bring down a Detroit-bound jetliner. That incident also spurred enhanced security screening that took effect today for people traveling to the United States from or through Yemen, Nigeria, Saudi Arabia and 11 other countries.

The official was not authorized to speak publicly about the watch lists and requested anonymity, but said that after the Dec. 25 incident counterterrorism officials reviewed information in TIDE on people from countries where terrorists have operated.

The Transportation Security Administration outlined the new security rules in a directive sent to airlines Sunday, but initial reports from several European countries indicated that they were still scrambling to digest and implement the new rules.