AMMAN - Syrian forces shot dead at least 24 civilians on Friday when they fired on demonstrators demanding international protection from President Bashar Assad's crackdown on seven months of unrest, activists and residents said.Most of the killings took place in the central cities of Hama, where Assad sent tanks and troops to crush dissent three months ago, and Homs, a center of increasingly armed opposition to his autocratic rule."A no-fly zone is a legitimate demand for Homs," read banners carried by protesters in the Khalidiya neighborhood.NATO jets played a central role in the overthrow of Libyan leader Muammar Gaddafi, but the Western alliance has shown no appetite to intervene in Syria to halt violence which the United Nations says has killed 3,000 people.Syria's opposition National Council has called for international protection. It has not explicitly requested military intervention, although street protesters have increasingly voiced that demand.