Sunni rebel extremists ambushed and killed more than two dozen Shiite volunteer militiamen late Sunday just outside the holy city of Samarra, the first such killings since Iraq’s government started mobilizing thousands of untrained Shiites to stop the insurgent advance threatening the country. That advance appeared to gain momentum elsewhere on Monday. Sunni insurgents took over the small city of Tal Afar, in northwestern Iraq, according to Iraqi security officials and residents, sending both Shiite and Sunni residents fleeing. In another sign of diminished confidence in the government of Prime Minister Nuri Kamal al-Maliki, the United Nations said Monday it had temporarily relocated 58 staff from Baghdad to Amman, Jordan. Farhan Haq, a spokesman for Secretary-General Ban Ki-moon, told reporters in New York that more United Nations staff members may be extricated in coming days. On Sunday, the State Department announced it had begun a partial evacuation […]