An Al Qaeda group claimed that it had attacked a U.S. intelligence officer after their surveillance showed increasing numbers of U.S. troops in the city of Aden. The new leader Prime Minister Hadi a vice-president under Saleh has vowed to continue the fight against Al Qaeda and other militant groups. He is supported by the U.S. even though he was the sole candidate for president and Saleh supporters and relatives still are the major group running the government.
The statement about the attack came from an AQAP (Al Qaeda in the Arabian Peninsula) website. The Pentagon has confirmed the attack but claims no one was killed. The website said of the intelligence officer:"He was targeted after increasing U.S. activity in Yemen in the light of new political circumstances, and the bringing of a large number of U.S. soldiers to Aden in particular," The site also urged a jihad against the Crusader enemy and to fight the American occupiers of Yemen.
A related militant group Ansar al-Sharia has claimed responsibility for a number of attacks that have killed so far at least 110 Yemeni soldiers in the south of Yemen.
The campaign of assassinations by U.S. drone strikes has been followed by increased militant activity involving taking over the entire province of Abyan at one point. There is also an active separatist movement in the south of the country. At one time the south was a separate country. For more see this article.
The U.S. has denied having any boots on the ground in Yemen. However, this attack in Aden shows this is simply false. The troops are probably special forces and for some reason they never count as boots on the ground. These troops are meant to be on secret missions and so their presence is simply not acknowledged.