KINSHASA, March 2 (Reuters) - U.N. Pakistani peacekeepers killed at least 50 to 60 militiamen in a clash in northeastern Congo on Tuesday, a week after nine Bangladeshi U.N. troops were killed there, senior U.N. sources said on Wednesday. "The number of militia dead is now 50, maybe 60, but there may be more because they were engaged by helicopters as well," said a senior source in the U.N. peacekeeping operation in the Congo. The clash happened 30 km (19 miles) outside the town of Bunia, the main city in the troubled Ituri region.