Yemeni officials say that militants have shot down an army helicopter, killing all eight people on board including a military commander. The officials say the helicopter was downed by a missile over the al-Qaida stronghold of Wadi Ubida in central Yemen. The helicopter was flying from the capital Sanaa to the province of Marib, officials said. The passengers were part of a military force guarding oil installations in the province. The officials spoke on condition of anonymity because they were not authorized to speak to the press. The attack comes at a time the U.S. and British embassies evacuated staff...