WASHINGTON, Aug 5: Travellers to the United States may now have to leave their cameras and walkmen home as airlines here prepare a new advisory for carry-on luggage.

The new advisory, expected to be issued soon, is being prepared under the instructions of the US homeland security department, which has asked American airlines and airports to pay extra attention to some type of personal carry-on items, such as cameras and electronics.

Over the weekend, the homeland security department also barred foreign travellers from stopping in the US on their way to another country unless they get a US visa before flying. The airlines industry says the restriction could cost US airlines as much as $200 million a year.

The concern about carry-on items follows the discovery of apparent prototype weapons in Al Qaeda safe houses overseas and interrogation of one of its operatives.

US officials say terrorists have considered trying to hide explosives in particular models of cell phones, cameras and simple electronic devices, such as radio boom boxes.