12 News KBMT and K-JAC. News, Weather and Sports for SE TexasMarine unit recalled as intel warns of possible revenge attacks

ABC NEWS - U.S. intelligence and law enforcement authorities warned today that al Qaeda may try to strike back at the U.S. for the death of Osama bin Laden and in a sign of the urgency, an elite unit of Marines who handle chemical and biological weapons attacks was recalled today from Japan.

The death of the world's most wanted terrorist has security experts at all levels of government concerned that bin Laden's loyal and fanatical followers could launch a series of deadly attacks.

"Though bin Laden is dead, al-Qaeda is not," said CIA Director Leon Panetta. "The terrorists almost certainly will attempt to avenge him, and we must—and will—remain vigilant and resolute. But we have struck a heavy blow against the enemy."

Former chief of staff to President George W. Bush, Andrew Card, told ABC News that reprisal attacks could already be planned.

"We have to be particularly vigilant about danger that is still out there. This act could cause people to do things people may have planned to do if this day came," Card said.

The Department of Homeland Security said the agency is on full alert.

"Our security posture, which always includes a number of measures both seen and unseen, will continue to protect the American people from an evolving threat picture both in the next days and beyond," said one Department of Homeland Security official.

Elite Marines Recalled From Japan

Already the 145 members of the Marines' elite Chemical Biological Incident Response Force are departing Japan, where they've been supporting radiation remediation efforts in the wake of the March earthquake that destroyed several nuclear reactors. The unit has been recalled to the United States, ready to respond to any potential emergency as a result of an attack.

Minutes after news of bin Laden's death becoming public, New York City officials placed police on high alert.

"While there is no information indicating a specific threat to New York City, members of the service are reminded to remain alert in the aftermath of the announcement that Osama Bin Laden has been killed," New York Police Commissioner Raymond W. Kelly told the 35,000 officers under his command.

Police in New York and Los Angeles said they would step up patrols near mosques and are warning of lone-wolf style attacks, by single individuals spurred to launch an attack.

In Philadelphia, Police Commissioner Charles Ramsey instructed officers to pay special attention to all mosques and synagogues with hourly checks.

Washington, D.C. police are increasing security along the Metro, the city's subway system, at hotels and at federal buildings.

The State Department told embassy officials and U.S. citizens around the world to be vigilant, particularly in those countries with a large U.S. military presence.

"We have to be on our toes and I have no doubt in my mind the intelligence community and law enforcement community and the FBI are working very hard to ensure this doesn't trigger attacks on Americans or American interests," Card said.

As officials take measures to secure American's safety, experts are warning citizens to be aware of possible security breaches.

Al Qaeda cells have used American passenger jets, including on 9/11 as weapons, and terrorists have attacked hotels, most famously in Mumbai, India, leading some experts to warn travelers to be particularly vigilant.

Travel analyst Joe Brancatelli cautioned travelers to be wary of airlines and hotels and warned of heighten security at airports.

"I would especially be wary about attacks on hotels. Even the best hotels are not secure because it is almost impossible to vet all visitors or effectively police public areas such as lobbies, back-of-the-house operations or even the roads directly surrounding the properties. In fact, more hotels have been attacked in recent years than airports and airlines," Brancatelli wrote in recent blog post.

 Bottom line: At least for now, proceed with extreme caution."

ABC News Richard Esposito contributed to this report.