WASHINGTON: The United States ordered Americans on Tuesday to leave Yemen “immediately” but also acknowledged that Al Qaeda cells in the Afghan-Pakistan region had been decimated.

“We are concerned about a threat stream indicating the potential for terrorist attacks against US persons or facilities overseas, especially emanating from the Arabian Peninsula,” State Department spokeswoman Jen Psaki said in a statement.

“As such, the department is taking appropriate steps to protect our employees, including local employees and visitors to our facilities.”

At the Pentagon, spokesman George Little said US military personnel remained “on the ground in Yemen to support the US State Department and monitor the security situation”. At another State Department briefing, Deputy Spokesperson Marie Harf said threat levels in the Afghan-Pakistan region had decreased but not enough to stop drone attacks.

“We have made a great deal of success against Al Qaeda core in Afghanistan and Pakistan (and) we have taken a number of steps to really decimate that group’s leadership, including, of course, most importantly, Osama bin Laden,” she said.

The focus, however, had shifted to the Middle East “where first on that list is always AQAP (Al Qaeda in Arabian Peninsula)”, she added.

Spokeswoman Psaki said the State Department had also ordered a reduction in the number of emergency US government personnel in Yemen.

“We are concerned about a threat stream indicating the potential for terrorist attacks against US persons or facilities overseas, especially emanating from the Arabian Peninsula,” she said.