MITROVICA, Serbia and Montenegro (Reuters) - NATO troops in Kosovo secured the fire-gutted Serbian church in the flashpoint town of Mitrovica on Saturday as dozens of Serbs crossed the bridge into the Albanian-dominated south to mark Orthodox Christmas. Split into Albanian and Serb halves, Mitrovica in northern Kosovo has seen some of the worst clashes since the end of the 1998-99 war and the town's division by French troops at the Ibar River. Serbs holding candles attend a service for Orthodox Christmas in the fire-gutted Serbian church in Mitrovica, 40 kilometres north of the Kosovo capital Pristina, January 7, 2006....