YEMEN - Security officials say four alleged al-Qaida members have been killed by a suspected U.S. drone in Yemen this morning.

The deaths come as all Americans have been ordered out of the country due to what they call an "extremely high" terror threat.

Officials say two U.S. military aircraft have now landed in Yemen to evacuate all Americans, including all non-emergency government personnel.

The head of al-Qaida reportedly sent messages to his deputy in Yemen saying "it's time again to attack Americans."

The messages were intercepted by intelligence officials.

Ayman al-Zawahri reportedly wants to free prisoners in Guantanamo and is calling for more unrest in Egypt.