Forensic investigators gather evidence at the scene of a bomb attack in the Yemeni capital Sanaa on Sunday after at least six people were killed and 26 wounded on a bus carrying members of the country's air force, witnesses and medics said.<br/> <br />There was no immediate claim of responsibility.<br/> <br />Security personnel stood guard while investigators at the scene picked through evidence near the attack site, with debris strewn across the tarmac.
