US President Barack Obama said Thursday he had not known about abuses by tax officials who targeted conservative groups until a report into the affair was leaked to the press last week. "I promise you this. The minute I found out about it, then my focus has been about making sure we get the thing fixed," Obama told reporters. The president spoke just a day after sacking acting Internal Revenue Service chief Steven Miller over reports that some agents had singled out groups affiliated with the ultra-conservative Tea Party and other right-wing causes.

President Barack Obama warned Thursday that a spate of sexual assaults in the military endangered US national security and vowed to do everything possible to fix the problem. Obama promised to act as he met Secretary of Defense Chuck Hagel, the highest ranking US military officer Army General Martin Dempsey, and the civilian and military bosses of each branch of the US military. The president said that the US military's strength lay in trust, teamwork and discipline.

Yemen's near-forgotten humanitarian crisis could sink its Arab Spring political transition, with a new constitution and elections expected by next year, a senior United Nations aid official warned Thursday. "In Yemen today, stability is threatened by the drastic humanitarian situation," said Ismail Ould Cheikh Ahmed, the UN's Yemen aid coordinator. He reeled off the stark data, saying that more than half of Yemen's 24 million people needed aid.