Awwal 11, 1432 / April 15, 2011, SPA -- U.N. Secretary-General Ban Ki-moon on Thursday said that an international military response saved thousands of lives in Libya but warned the humanitarian situation is deteriorating there and called for a similar international response to avert a major crisis. "Within Libya itself, the picture is especially grave," Ban told the Cairo Conference on Libya, which he co-convened with the League of Arab States to discuss the ongoing fighting in the North African nation pitting government forces against rebels seeking the ouster of Colonel Muammar Gaddafi. In the cities of Misrata, Brega and Zintan, where the fighting has been particularly intense, access to basic services and basic commodities such as food, water and health care has been largely cut off, the U.N. chief said. An estimated 500,000 people have left Libya since the conflict began earlier this year and many remain stranded at camps and transit points in neighboring countries, the U.N. has said. Ban said he intends to establish an international presence in the capital, Tripoli, as soon as possible, and that U.N. Under-Secretary-General for Humanitarian Affairs Valerie Amos may visit the city in light of the dire situation. "I have also called on all neighboring countries to keep their borders open to receive those fleeing the conflict," he said. "We must be careful not to allow large concentrations of refugees awaiting evacuation to build up along the border, particularly given the fragility of the situation in the region."