<sod >The Prime Minister David Cameron has described the air disaster as "absolutely appalling, shocking [and] horrific" and called for those responsible "to be held to account" after a chairing a meeting of the Government's Cobra emergency committee.< eod>< sod > " Calling for an immediate ceasefire in Ukraine, Obama demanded a credible investigation into the incident. "We're going to make sure that truth gets out," he said, having called the crash a "terrible tragedy" on Thursday evening. Earlier in the day, Prime Minister David Cameron had described the air disaster as "absolutely appalling, shocking [and] horrific" and called for those responsible "to be held to account" after a chairing a meeting of the Government's Cobra emergency committee.< eod>