Obama warns US of 'credible' jet bomb threat

The President said the packages, which originated in Yemen, had both contained explosive material and the targets appeared to be two synagogues in Chicago.

Mr Obama spoke of the need to tackle an al-Qaida offshoot in the Yemen and urged the public to be "vigilant".

Speaking yesterday in the White House, President Obama said: "Last night and earlier today our intelligence and law enforcement professionals working with our friends and allies identified two suspicious packages bound for the US – specifically, two places of Jewish worship in Chicago.

"Those packages have been located in Dubai and East Midlands Airport in the UK.

"Initial examination of those packages has determined that they do apparently contain explosive material."

He appears to have contradicted earlier suggestions that the package found in Britain did not contain explosives.

Mr Obama said he had instructed officials to take "whatever measures were necessary" to protect Americans, and planes in Newark and Philadelphia had been searched as part of tougher cargo screening.

"We will continue to pursue additional protective measures for as long as it takes to ensure the safety and security of our citizens," he added.

"I have also directed that we spare no effort in investigating the origins of these suspicious packages and their connection to any additional terrorist plotting."

Mr Obama said Yemen president Ali Abdullah Saleh had pledged "full co-operation".

"Going forward we will continue to strengthen co-operation with the Yemen government to disrupt plotting by al-Qaida in the Arabian Peninsula, and to destroy this al-Qaida affiliate."

Police were called to a freight distribution centre at East Midlands Airport early yesterday morning after officials raised concerns about a flight that originated in Yemen.

Soon afterwards, a suspect device was found in Dubai.

In the US two United Parcel Service jets in Philadelphia and a third jet in Newark, New Jersey, were moved away from terminal buildings.

In New York, police were examining a suspect package from a UPS truck, although it was later described as a package of bank receipts. An Emirates flight from Dubai was escorted safely into New York by fighter jets.

US jets also escorted flights that had originated in the Yemen as a precaution, but late last night it appeared that no suspect devices had reached the US.

Home Secretary Theresa May said: "At this stage there is nothing to suggest that any location in the UK was being targeted.

"We are urgently considering what steps need to be put in place regarding security of freight originating from Yemen."

Concerns have been growing about the threat posed by Yemen-based terrorists.

Direct flights to the UK were halted in January after a plot to bomb a plane bound for Detroit was foiled. In April, an al-Qaida suicide bomber almost succeeded in assassinating Tim Torlott, Britain's ambassador to Yemen and earlier this month, terrorists targeted Fiona Gibb, the deputy chief of the UK's embassy in the capital Sana'a.