An unknown number of hostages are still being held by Islamist gunmen who are locked in a stand-off with security forces inside Nairobi\'s Westgate shopping mall, the Kenyan government said early Sunday. \"Hostage numbers still unknown, but they are in several locations. No communication as yet. Upper levels (of the mall) have been secured,\" the government\'s National Disaster Operation Centre said in a situation update posted on Twitter.