GAZA CITY: Israel assassinated a Hamas strongman on Thursday in its first assault on the top leadership of the territory s ruling group, escalating a crushing aerial offensive even as it declared itself ready to launch a ground invasion. The airstrike targeted the eight-story apartment building that was home to Nizar Rayan, 52, ranked among Hamas top five decision-makers in Gaza. The attack killed 12 other people including two of Rayan s four wives and four of his 12 children, Palestinian health officials said. While escalating its 6-day-old military offensive against Hamas in Gaza, Israel also appeared to be sounding out a possible diplomatic exit from its campaign by demanding international monitors as a key term of any future truce with Hamas in the Gaza Strip. Warplanes bombed the parliament building in Gaza City on Thursday and Israeli ships attacked coastline positions. International agreement to set up such a force would give Israel a way to end its devastating, 6-day-old offensive against Hamas, even as thousands of Israeli ground troops massed along the border in anticipation of a possible land invasion. So far, the campaign to crush rocket fire on southern Israel has been conducted largely from the air, and a poll on Thursday showed most Israelis aren t eager to see a ground push. Military spokeswoman Maj. Avital Leibovich said preparations for a ground operation were complete. The infantry, the artillery and other forces are ready. They re around the Gaza Strip, waiting for any calls to go inside, Leibovich said. More than 400 Gazans have been killed and some 1,700 have been wounded since Israel embarked on its aerial campaign on Saturday, Gaza health officials said. The UN says the Gaza death toll includes more than 60 civilians, 34 of them children. Three Israeli civilians and one soldier have also died in rocket attacks that have reached deeper into Israel than ever before. We have no interest in a long war. We do not desire a broad campaign. We want quiet, Prime Minister Ehud Olmert told a meeting of mayors of southern Israeli cities Thursday. We don t want to display our might, but we will employ it if necessary. Olmert, who rebuffed a French proposal for a two-day timeout, won t agree to a truce unless international monitors take responsibility for enforcing it, government officials said. He s made this point in talks with US Secretary of State Condoleezza Rice and other world leaders who are pressing for an end to the violence, they added. They spoke on condition of anonymity because the talks were confidential. -AP International intervention helped Israel to accept a truce that ended its 2006 war with Lebanese Hezbollah guerrillas, when the UN agreed to station peacekeepers to enforce the terms. This time, Israel isn t seeking a peacekeeping force, but a monitoring body that would judge compliance on both sides. The idea was floated before the offensive but did not gain traction because of the complications created by the existence of rival Palestinian governments in the West Bank and Gaza, defense officials said. Gaza has been under Hamas rule since the group overran it in June 2007; the West Bank has remained under the control of moderate Palestinian President Mahmoud Abbas, who has been negotiating peace with Israel for more than a year but has no influence over Hamas. Bringing in monitors would require cooperation between the fierce rivals. A Abbas confidant said the Palestinian president supported the notion of international involvement. We are asking for a cease-fire and an international presence to monitor Israel s commitment to it, aide Nabil Abu Rdeneh said. Israeli Cabinet ministers have been unswayed by a flurry of diplomatic activity meant to end the violence, which is to include a whirlwind trip around the region next week by French President Nicolas Sarkozy. Instead, they authorized the military to push ahead with its campaign against insurgents, who fired 21 rockets into Israel by midday Thursday, according to police. No injuries were reported, but an eight-story house in Ashdod, 37 km from Gaza, was hit. France had proposed a 48-hour suspension of the operation to allow humanitarian supplies into Gaza, but Olmert said the time wasn t ripe. A separate proposal by Turkey and Egypt, two of Israel s few allies in the Muslim world, also seemed to be attracting little serious study in Israel or Gaza. UN chief Ban Ki-Moon on Wednesday urged an immediate ceasefire on both sides, saying, The parties must step back from the brink. The UN Security Council, meeting for emergency consultations Wednesday night, rejected an Arab request for a legally binding resolution that would condemn Israel and halt its attacks. The US called a draft resolution unbalanced because it made no mention of halting Hamas rocket fire at Israeli towns - the immediate cause behind the massive Israeli air offensive. Echoing Israel s cool response to truce proposals, a senior Hamas leader with ties to its military wing, Osama Mazini, said Wednesday that now was not the right time to call off the fight. Hamas was unhappy with the six-month truce that collapsed just before the fighting began because it didn t result in an easing of Israel s crippling blockade on Gaza. Israel and Egypt blockaded Gaza after Hamas violently seized control of the territory in June 2007, and have cracked open their borders only to let in limited amounts of humanitarian aid. Huge explosions shook Gaza City on Thursday as Israeli planes targeted three government buildings, including the parliament. Hospital officials said 25 wounded were evacuated from nearby houses. The military said aircraft also bombed smuggling tunnels along the Gaza-Egypt border, part of an ongoing attempt to cut off Hamas last lifeline to the world outside the embattled Palestinian territory. Aircraft also went after Hamas police and their vehicles. Two people were killed when a car was blown up. One pre-dawn strike targeting the house of a Hamas operative in northern Gaza killed a 35-year-old woman and wounded eight people, a Gaza Health Ministry official said. Israeli ground forces, meanwhile, were putting the final touches on preparations for a possible ground invasion, which would have to be ordered by Israel s Cabinet to go ahead. The thousands of troops who are to take part have been moved to the border, along with armored vehicles and artillery pieces. Israelis are not eager to see the operation expand beyond the air-based campaign, a poll Thursday showed. The survey of 472 people showed that 52 percent want the air assault to continue, while only 19 percent wanted to see a ground offensive. Twenty percent favored a cease-fire. The same poll showed dovish and centrist parties would get 60 seats in Israel s 120-seat parliament if elections were held today, up from 53 before the operation. The big winner was the centrist Labor, led by Defense Minister Ehud Barak, the Gaza operation s mastermind. Hardline and religious parties dropped from 65 to 60. The Dialog company poll appeared Thursday in the daily Haaretz. It had a margin of error of 4.6 percentage points. In five days of raids, Israeli warplanes have carried out some 500 sorties against Hamas targets, and helicopters have flown hundreds more combat missions, a senior Israeli military officer said on condition of anonymity in line with military regulations. -Amy Teibel reported from Jerusalem.