Syrian forces loyal to President Bashar al-Assad have fired Scud missiles at rebel fighters in recent days, Obama administration officials said on Wednesday. The move represents a significant escalation in the fighting, which has already killed more than 40,000 civilians in a nearly two-year-old conflict that has threatened to destabilize the Middle East. One American official, who asked not to be identified because he was discussing classified information, said that missiles had been fired from the Damascus area at targets in northern Syria. “The total is number is probably north of six now,” said another American official, and that the...