US officials tightened security measures for US-bound airline passengers on Sunday, including mandatory enhanced screening of all travellers from 14 nations, some on a terrorism blacklist.
Ten days after a failed Al-Qaeda bid to blow up a Northwest flight from Amsterdam to Detroit, US transport officials said the new measures were part of a drive to put in place "long-term, sustainable security measures."
All passengers flying into the United States from abroad will be subject to random screening or so-called "threat-based" screens, the Transport Security Administration (TSA) said in a statement.
But it further mandated that "every individual flying into the US from anywhere in the world traveling from or through nations that are state sponsors of terrorism or other countries of interest will be required to go through enhanced screening."
The tough rules go into effect from midnight Sunday and follow the botched Christmas Day bombing blamed on a 23-year-old Nigerian who had recently traveled to Yemen to train with Al-Qaeda. He boarded the flight at Amsterdam's Schiphol airport after flying in from Lagos, Nigeria.
Cuba, Iran, Sudan and Syria are currently the only four countries deemed by the State Department to be state sponsors of terrorism.
But a senior administration official told AFP the stringent measures would include all passengers traveling from or via a total of 14 countries, including Afghanistan, Libya, Nigeria, Pakistan, Somalia and Yemen.
He refused to reveal the remaining four nations, but The New York Times and Washington Post quoted government officials identifying them as Saudi Arabia, Algeria, Lebanon and Iraq.
All travelers from or via the targeted countries would be subjected to extra security measures including body pat-downs, advanced screening and property inspections.
Imaging and explosive detection technology might also be used, he said.
TSA said the new measures were being introduced "because effective aviation security must begin beyond our borders."
It added they were "developed in consultation with law enforcement officials and our domestic and international partners."
Nigerian suspect, Umar Farouk Abdulmutallab, is due to be arraigned in Detroit on Friday following the botched plane bombing in which he was badly burned.
He is allegedly to have tried to blow up the airliner as it approached Detroit by setting off explosives stitched into his underwear, and which were not detected by the metal detectors.
The failed attack has led to security jitters around the world, and on Sunday, the United States and Britain closed their embassies in the Yemeni capital Sanaa.
President Barack Obama's top counter-terrorism advisor warned Al-Qaeda could be planning another assault.
There are "indications that Al-Qaeda is planning to carry out an attack against (a) target inside of Sanaa, possibly our embassy," John Brennan, told CNN.
Obama has directly linked Al-Qaeda in the Arabian Peninsula (AQAP), a Yemen-based cell of Osama bin Laden's group, to the failed bombing of the Northwest jet carrying 290 people.
He has ordered two reviews into the security lapses which nearly led to another tragedy in a nation still scarred by the Al-Qaeda attacks of September 11, 2001.
Obama, who was due to end his Christmas vacation in Hawaii later Sunday to return to Washington, will huddle with his top security advisors on Tuesday to review the findings of the investigations.