PESHAWAR, Pakistan (Reuters) -A 7-km (4-mile) lake in northern Pakistan, created by a mountain mudslide, is threatening to burst and unleash potentially "catastrophic" floods downstream, officials warned on Saturday. The mud flow descended into the main Ghizer River channel and blocked it completely on Friday, creating the lake in Gilgit Baltistan province, the National Disaster Management Authority said. The new lake "can cause a catastrophic flood", said Zakir Hussain, director general of the Provincial Disaster Management Authority.