The U.S. Federal Bureau of Investigation is in Yemen helping the government probe last week's rocket and mortar attack on the president's palace, according to the Voice of Yemen website.

Six high-level government officials were wounded in addition to President Ali Abdullah Saleh, who himself sustained serious injuries, including burns over 40 percent of his body and a piece of shrapnel embedded under his heart. All were flown to nearby Saudi Arabia for medical treatment. Power was temporarily transferred to the nation's vice president but few believe that Saleh will return.

Within days an FBI team arrived in the capital Sana'a to aid Yemeni law enforcement investigators in the probe. Yemen is a close ally of the United States, and Saleh has worked closely with the Americans in fighting the Al Qaeda terrorists who have repeatedly tried to set up bases in his country as chaos increases. In the meanwhile, clashes intensify between government troops and rebel forces.

Initial beliefs that the rival Hashid tribal confederation headed by powerful tribal leader Sadeq al-Ahmar was behind the attack are now being questioned, and other suspects are being considered as well – among them members of Saleh's own inner circle, and terrorists from Al Qaeda in the Arabian Peninsula (AQAP).

The U.S. has attempted several times to assassinate American-born Muslim cleric Anwar al-Awlaki, who leads AQAP in southern Yemen from headquarters based in the Abyan province along with other terrorists.

American military drones and fighter jets have conducted a covert campaign of air strikes on the region over the past several weeks in an attempt to take out Al Qaeda bases as well as al-Awlaki.