GAZA CITY (Agencies) - Israeli warplanes killed three young brothers and demolished a mosque in Gaza on Friday as Hamas vowed to avenge the deadly week-long offensive on its embattled stronghold. Israeli PM Ehud Olmert met with senior ministers as tanks and troops waited on the Gaza border where a ground offensive is expected to start within days. Protests at the deadly bombardments spiralled in the Muslim world after Friday prayers, denouncing Israeli barbarism and demanding immediate halt to the air raids. Seven days into the offensive, Israeli jets staged more than 30 new raids on the densely populated territory, which it said targeted rocket launching sites and Hamas buildings. A missile fired by an Israeli jet slammed into a house in southern Gaza, killing three boys, aged from seven to 10. It was one of more than 40 fresh raids carried out in the overcrowded enclave on Friday. Jests bombed a mosque in the northern town of Jabaliya it alleged had been used to store weapons and destroyed the homes of more than a dozen Hamas operatives. In airstrike after airstrike early Friday, Israeli warplanes hit some 20 houses believed to belong to Hamas activists and members of other armed groups, Palestinians said. Since Israel unleashed its air and sea campaign, at least 430 Palestinians have been killed, including 65 children, and 2,250 others wounded, according to Gaza medics. Thousands of Hamas faithful attended the funeral of Nizar Rayan - a firebrand hardliner who was killed with his four wives and 11 children on Thursday. Hamas vowed to avenge the death of the most senior Hamas leader to be killed in the offensive and the most senior Islamist killed by Israel since Abdel Aziz al-Rantissi in 2004. "I call on the resistance to continue pounding Jewish settlements and cities," said Sheikh Abdelrahman al-Jamal as Rayan. "We will remain on the path of jihad." Hamas called a "Day of Wrath" against Israel, which brought thousands of protesters out onto the streets of Gaza and the occupied West Bank. Police fired teargas at rock throwing youths in annexed east Jerusalem. With a ground offensive widely expected and no ceasefire in sight, the Israeli army opened a border crossing to allow an estimated 400 foreigners leave the battered enclave. Israeli warplanes bombarded the Gaza Strip's defunct international airport along the Palestinian territory's border with Egypt, Hamas and witnesses said. They said one person was injured in the bombing of the airport facility located in close proximity to both the Egyptian and the Israeli borders. Hamas fired more than 30 rockets into Israel, but no casualties were reported. Israeli Foreign Minister Tzipi Livni reiterated that Israel was not yet ready for a truce after talks in Paris on Thursday with President Nicolas Sarkozy and other French leaders. "The question of whether it's enough or not will be the result of our assessment on a daily basis," she said. Meanwhile, Hamas supremo Khaled Meshaal on Friday warned Israel that a "black destiny" awaits the Jewish state if it launches a ground offensive into the Gaza Strip. "If you commit the stupidity of launching a ground offensive then a black destiny awaits you," the Syria-based Meshaal said in a pre-taped speech aired on Al-Jazeera television. "You will soon find out that Gaza is the wrath of Allah," said Meshaal. The UN World Food Programme called the situation in Gaza "appalling... many basic food items are no longer available on the market."