Washington, Dec 27 - Travellers to the US from abroad were advised Saturday to allot extra time for check-in as Washington upped the security requirements to board a US-bound plane.

The new restrictions follow Christmas Day's foiled attempt by a Nigerian terrorist suspect to explode Northwest Flight 253 from Amsterdam as it was landing in Detroit with about 300 people on board.

Homeland Security Secretary Janet Napolitano, in a statement, said the new measures would be "unpredictable", and would also be tightened for domestic travellers inside the US.

Anecdotal reports described how screeners have required a mother travelling with a baby to provide samples of each and every bottle of milk she was carrying.

Another man told CNN that screeners had taken apart his laptop case.

There were reports that passengers would now be required to remain seated for an hour before landing, with no access to toilets or luggage stored above the seats. Passengers may not be able to have pillows or blankets in the hour before landing.

In addition, there were reports that the GPS systems displayed on viewing screens in passenger planes are to be shut off to deny passengers orientation about the progress or position of the plane.

US federal officials Saturday brought criminal charges against Umar Farouk Abdulmutallab, 23, a Nigerian who tried to set off an explosion using PETN, also known as pentaerythritol, a high explosive.

Abdulmutallab had gone to the bathroom for about 20 minutes, came back to his seat and complained of stomach ache, then covered his lap with a blanket. Soon after, passengers noted smoke and flames coming from his seat, and rushed to subdue the suspect as well as put outthe fire.

Governments have increasingly tightened security measures since the 2001 terrorist attacks on the US, when hijackers commandeered four passenger planes and killed nearly 3,000 people.

Since terrorist Richard Reid, a Briton, tried to blow up an American Airlines plane in December 2001 with PETN explosives molded into his shoes, travellers must remove their shoes for examination.

Since the 2006 foiled attempt in London to blow up seven intercontinental airliners with liquid explosives, travellers are limited in what sort and amount of liquids they can carry on board and can no longer carry their own food or water. (dpa)