The greying of Osama bin Laden ... the FBI issued the images at centre and right, altered by forensic artists, showing how the al-Qaeda leader may have changed his appearance.

The greying of Osama bin Laden ... the FBI issued the images at centre and right, altered by forensic artists, showing how the al-Qaeda leader may have changed his appearance. Photo: Reuters, AFP

LONDON: The FBI has published fresh photographs of Osama bin Laden in an attempt to track down the al-Qaeda leader.

In one ''aged progressed'' mugshot, he is portrayed in Western clothes with wavy grey and black hair and a trimmed beard; another shows him in his traditional outfit, with a white turban and a flowing, but greyer, beard.

Forensic artists used digital enhancement to modify bin Laden's features in an attempt to show what he might look like now.

The FBI also published ''aged progressed'' mugshots of another 17 terrorists wanted by the US, which can be seen on the State Department website.

The photos were released as the US announced it would further strengthen air security. The new measures are to be introduced after intelligence reports that individuals associated with al-Qaeda in Yemen were seeking to attack planes, US interests overseas and targets in the US, said an official who spoke on condition of anonymity.

They include randomly screening more passengers, more federal air marshals and including more people on the Government's terrorism watch list, the Homeland Security Secretary, Janet Napolitano, said.

''We are taking an additional set of aviation-security precautions to protect the American people,'' she said in a statement.

The Transportation Security Administration, which Ms Napolitano oversees, increased security restrictions after the failed attempt on December 25 to blow up a Detroit-bound Northwest airliner.

Travellers in the US may notice more random screening, officers who specialise in detecting suspicious behaviour and wider use of bomb-detection equipment, said Greg Soule, a security spokesman. Security was being increased throughout airports.

''Passengers travelling should not expect to see the same thing at every airport,'' he said.

Guardian News & Media, Bloomberg