Six killed in bomb attack on Yemen air force bus SANAA (Reuters) - At least six people were killed and 26 wounded on Sunday in a bomb attack on a bus carrying members of Yemen's air force to their base in the capital Sanaa, witnesses and medics said. Ameen Saree, an air force officer who rushed to the scene, said a bomb had been planted in the vehicle. "The bomb exploded in the rear part of the bus and six of our colleagues were immediately killed," Saree told Reuters. The rest have been injured and are being treated in hospitals. Yemen has been gripped by turmoil since pro-democracy protests against former President Ali Abdullah Saleh broke out in early 2011. Attacks against military personnel are more common in the largely lawless south and east where an Islamist insurgency is still raging. In May 2012, a suicide bomber in an army uniform killed more than 90 soldiers rehearsing for a parade in the heart of Sanaa. Yemen, one of the poorest countries in the Arab world and next door to world's top oil exporter Saudi Arabia, is also battling a powerful branch of al Qaeda that U.S. officials say is the most dangerous of the global network. U.S. and other Western nations shut their diplomatic missions across the Middle East, North Africa and Asia after a warning of a possible militant attack. Writing by Mahmoud Habboush, Editing by Yara Bayoumy and Andrew Heavens