Israeli tanks have rolled into densely populated parts of Gaza city as the fight with Hamas intensifies. The Islamist militants fought with Israeli forces backed by helicopter gunships and naval fire in what appeared to be the most ferocious fighting since Israel sent ground troops into the Palestinian enclave ten days ago. The Palestinian death toll in the 18 days since Israel began an air offensive has passed 900, including many civilians. Israel has lost ten soldiers and three civilians to mortar and rocket fire from coastal Gaza. Israeli military spokesman Brigadier General Avi Benayahu said Israel was "tightening the encirclement" of Gaza City and has moved up reserve units to free up regular troops for a push into the city. United Nations Secretary-General Ban Ki-moon headed to the region to press for a truce in a week of talks with leaders in Egypt, Israel, Jordan and Syria.