Israeli troops have fought fierce gunbattles with Hamas fighters as army reservists entered the air and ground assault in Gaza. The Palestinian death toll in the 17-day-old conflict has passed 900, including 380 civilians, while around 3,600 people have been wounded. Thirteen Israelis have died, including ten soldiers as well as three civilians who were hit by rockets. Israeli forces are still holding back from a possible third stage of their offensive against Palestinian militants - a push into the city of Gaza and other urban areas. In Gaza, Israeli soldiers battled Hamas militants east and north of the rubble-strewn city in what residents described as ferocious fighting. More than 25 airstrikes were carried out - fewer than previous days - which targeted Hamas gunmen, weapons caches, rocket and mortar launching positions and a smuggling tunnel under Gaza's border with Egypt, the Israeli army said. On Sunday, Israeli Prime Minister Ehud Olmert, Defence Minister Ehud Barak and Foreign Minister Tzipi Livni met and decided to tighten pressure on Hamas by using the country's sizeable army reserves. The move risks higher Israeli military casualties as well as even heavier losses among the 1.5 million Palestinians packed into the tiny coastal enclave. Israeli warplanes have repeatedly bombed the so-called Philadelphi corridor along Gaza's nine-mile border with Egypt and used "bunker buster" munitions that explode underground and cause shockwaves to try to collapse the tunnels. Israel, which rejected last week's UN ceasefire resolution as unworkable, wants a halt to rocket attacks and measures to stop Hamas from rearming via the cross-border tunnels. Mr Barak said: "We are determined to achieve the goals we have set for ourselves at the beginning of the operation, and are in parallel examining the diplomatic course as well." Hamas leader Khaled Meshaal said his Islamist group would not consider a ceasefire until Israel ended its air, sea and ground assault and lifted its blockade of Gaza. A Hamas delegation is in Cairo for talks on an Egyptian truce plan.