Hundreds of evacuees from this besieged city were detained by the Syrian regime as soon as they were rescued, said the top United Nations official here, who said the U.N. now has no control over their fate. The disclosure came as President Barack Obama and his visiting French counterpart, François Hollande, expressed dismay in Washington about the humanitarian crisis in Homs and elsewhere in Syria. Mr. Obama described the situation as “horrendous” and asserted that the country was “crumbling” as he put the responsibility partly on Syrian ally Russia. Most member states of the U.N. Security Council want to pass a resolution requiring that humanitarian aid be allowed into besieged areas of Syria. But, “Russia is a holdout,” Mr. Obama said. “They cannot say that they are concerned about the well-being of the Syrian people when there are starving civilians,” he said, adding not only Syria is responsible, […]