President Barack Obama himself is keeping a close tab on the developments related to the threat. National Security Advisor Susan Rice held a meeting of top US national security officers to review the potential terror threat coming from the Arabian Peninsula. "The President has received frequent briefings over the last week on all aspects of the potential threat and our preparedness measures," a White House statement said.

Obama had instructed his national security team to take all appropriate steps to protect the American people in light of the threats, the statement said.

"Given nature of the potential threat, throughout the week, Assistant to the President for Homeland Security and Counter-terrorism Lisa Monaco has held regular meetings with relevant members of the inter-agency to ensure the US Government is taking those appropriate steps," the White House said.

Rice on Saturday chaired a meeting with the Principals Committee to review the situation and follow-up actions. Congressman Peter King, chairman of the Sub-committee on Counter-terrorism and Intelligence, said the threat was very specific, but he did not divulge any details.

"We're not certain exactly where something might happen but it's very specific as to when and it's also very specific as to the fact that it is going to happen, so we have to be on alert everywhere," King told a news channel.

In view of the terrorist threat, the Department of Homeland Security had Saturday increased security measures at airports, train stations and other transportation hubs. It expanded scrutiny of visitors coming into the US.

According to an official from the Department of Homeland Security, such measures are being taken out of an abundance of caution.

"As always, our security posture, which at all times includes a number of measures both seen and unseen, will continue to respond appropriately to protect American people from an ever-evolving threat picture," the official said.

On Friday, the State Department had issued a world-wide terror alert for its citizens, particularly in the Middle East and North Africa, and possibly occurring in or emanating from the Arabian Peninsula.

Canada shuts down its Dhaka mission

Ottawa: Canada shut its mission in the Dhaka Sunday, a spokesman said, citing security reasons amid global concern over terror threats."We take the safety and security of our personnel and our missions overseas very seriously," said Emma Welford, a spokeswoman for Canada's Department of Foreign Affairs, Trade and Development. AP

Yemeni forces on alert at embassies

Sanaa: Yemeni security forces were on high alert Sunday around Western embassies in Sanaa which are to remain closed following a US warning of a major al-Qaeda attack. Special forces with armoured personnel were stationed outside the US embassy and the missions of Britain, France and Germany. PTI