Driven underground by Israel's vow to wipe out the remaining Hamas leadership by air strike, Abdel Aziz al-Rantissi emerged briefly for a fiery open-air speech on Sunday before 5,000 people in the main courtyard of Gaza City's Islamic University.

Israeli warplanes roared overhead at one point during his address and the crowd gazed skyward nervously. But Rantissi seemed unmoved and kept speaking. He was flanked by armed bodyguards and stood on a podium close to the throng.

Rantissi, who last June survived an Israeli missile strike of the kind that killed Hamas founder Sheikh Ahmed Yassin a week ago, said Thursday's US veto of a UN Security Council resolution condemning Yassin's assassination was no surprise.

"We realise that Bush is the enemy of God, the enemy of Islam and Muslims. America declared war on God. (Israeli Prime Minister Ariel) Sharon declared war on God and God declared war on America, Bush and Sharon," he said.

"The war of God goes on against them and I can see victory arising from the land of Palestine by the hand of Hamas," Rantissi said of the militant faction behind suicide bombings that have killed hundreds of Israelis.

A grassroots movement challenging mainstream Palestinian authority and its policy of negotiations with Israel, Hamas seeks not just to roll back Israeli occupation in Gaza and the West Bank but to destroy the Jewish state.