Airlines with direct flights to the United States have been told to tighten their screening of mobile phones in response to increased terrorist threats. US officials singled out Apple iPhones and Samsung Galaxy models for extra security checks.

They will apply to US-bound direct flights from Europe, the Middle East and Africa, the officials said. The new precautions come in response to requests from US authorities, who fear attacks on planes flying to America.

US security officials said they fear bombmakers from the Yemen-based al-Qaeda in the Arabian Peninsula (AQAP) have worked out how to turn the phones into explosive devices which can avoid detection.

They also are concerned that hard-to-detect bombs could be built into shoes. A US official said that other electronic devices carried by passengers also are likely to receive more intense scrutiny.

Airlines or airport operators that fail to strengthen security could face bans on flights entering the US.

On Thursday, the US Homeland Security Department announced on plans to step up general security checks - but offered few details on how airlines and airports will implement them.

An official familiar with the issues said the US believes that while it is possible there may be some additional delays at security checkpoints, at most major airports passengers will not be seriously inconvenienced.

The official said most passengers taking long-distance flights arrive well in advance of scheduled departures, leaving time for extra screening.

But he said the US could not rule out disruptions in countries where airport infrastructure and security procedures are less sophisticated.

Yesterday the Dublin Airport Authority (DAA) said they are working with the Department of Transport closely - but there will be no direct effect on passengers for the moment.