At least seven people have been killed in a fresh US assassination drone attack in the southern Yemeni governorate of Shabwa, local sources say.Security officials said missiles fired by a US drone destroyed two vehicles in the town of Nasab early on Wednesday, killing seven people in the vehicles. The attack was the fifth of its kind in Yemen in less than two weeks and brought to 24 the number of people killed in US air raids since July 28. The attack comes a day after the US and its allies pulled diplomats out of Yemen due to a threatened attack by al-Qaeda in the country. According to media reports, the pullback was ordered after US intelligence intercepted messages exchanged between al-Qaeda leader, Ayman al-Zawahiri, and Nasir al-Wuhayshi, the leader of al-Qaeda's Yemen offshoot. Zawahiri had ordered Yemen's al-Qaeda to carry out an attack as early as last Sunday. The United States often uses its assassination drones to hit targets in Yemen and some other countries, including Pakistan and Afghanistan. Washington claims the drones target "militants," but the facts on the ground show that civilians are frequently killed in the airstrikes. According to the Washington-based New America Foundation, the US killer drone attacks in Yemen almost tripled in 2012. In April, Yemeni National Organization for Defending Rights and Freedoms said the US drones had conducted more than 80 attacks in the country in 2012. Washington has come under fire for increasing the drone attacks in Yemen. Yemenis have held demonstrations on several occasions over the past months to condemn the US for violating Yemen’s sovereignty by the drone strikes.