Yemen drone strike kills four militants, Americans asked to leave

All Americans citizens have been urged to leave Yemen immediately following a drone strike that killed four al-Qaida militants Tuesday after the United States announced a heightened security alert.

Yemeni officials have said that four drone strikes have taken place in the nation in the past 10 days. The pair of drones that struck Tuesday are suspected to belong to the U.S. None of the people killed were on the country's most-wanted list, security officials confirmed.

According to CNN, it is unclear if the strikes were related to the added security alert imposed by the U.S. after officials intercepted a message from al-Qaida leader Ayman al-Zawahiri to operatives in Yemen telling them to "do something."

The message was reportedly addressed to Nasir al-Wuhayshi, the leader of al-Qaida in the Arabian Peninsula.

Two U.S. military transport aircraft landed in the Yemen Tuesday to facilitate the evacuation of U.S. personnel.

"In response to a request from the U.S. State Department, early this morning the U.S. Air Force transported personnel out of Sana'a, Yemen, as part of a reduction in emergency personnel," Pentagon press secretary George Little said in a statement.

The British Foreign Office also announced that all British Embassy staff in Yemen would be temporarily withdrawn.

Little added that a few members of the Department of Defense would stay in Yemen following the evacuation to monitor the security situation.