UN chief Ban Ki-moon was set Wednesday to announce a UN probe into the assassination of former Pakistani premier Benazir Bhutto during a flying visit to Islamabad, the foreign ministry said. Ban's visit here -- his first since taking office two years ago -- after a stopover in Afghanistan comes two days after unidentified gunmen kidnapped a top UN official in Quetta two days ago. It also comes amid rampant unrest in Pakistan's border areas, with Taliban rebels disrupting a crucial NATO supply route into Afghanistan and government forces engaged in bloody fighting in the northwest Swat valley. The foreign ministry says Ban's talks will focus on the expected formation of a UN commission to investigate the December 2007 assassination of Bhutto, a two-time prime minister who was killed at a campaign rally.