The Hamas leader-in-exile, Khaled Meshaal, has warned Israel that it would face a "black destiny" if it launched a ground offensive on Gaza.
"If you commit a foolish act by raiding Gaza, who knows, we may have a second or a third or a fourth Shalit," Meshal said, referring to Israeli soldier Gilad Shalit, who was abducted by Gaza militants more than two years ago. "
Speaking publicly for the first time since Israeli air strikes started a week ago, he said Hamas resistance and infrastructure were intact.
His remarks came as the UN warned of a worsening humanitarian crisis in Gaza. The UN said it believed 25% of more than 400 Palestinians said killed by Israeli action so far were civilians.
In a pre-recorded statement broadcast on al-Jazeera TV, Damascus-based Khaled Meshaal, said Israel would be making a "foolish mistake" if it sent tanks into Gaza. "We will not break, we will not surrender or give in to your conditions," Mr Meshaal said in a speech aimed at the Israelis, the Palestinians and the wider Muslim world.
Al-Jazeera reaches millions of people across the Arabic-speaking world in the Middle East and beyond.
To them, Mr Meshaal said this was not a battle against Hamas alone, but against the entire umma, or nation - analysts say an apparent reference to a populist Islamist idea that the Palestinians are defending the Muslim world against a modern form of Crusades.
The UN said the Israeli military escalated its offensive against the Hamas leadership in Gaza on Friday, targeting the homes of more than 20 Hamas officials in its latest air strikes.
In response, Palestinian militants fired on Israel, launching more than 60 missiles in 24 hours, injuring four people in the southern city of Ashkelon.
BBC Middle East Editor Jeremy Bowen says a week of bombardment has not been able stop militant rocket attacks, and Israel now has to decide whether to send in ground troops.
Israel is tightening security ahead of demonstrations called by Palestinian militant group Hamas in protest at Israel's bombardment of the Gaza Strip.H
Hamas leaders have urged Palestinians to observe a "day of wrath", after seven days of violence in Gaza.
Early on Friday, Israel bombed more targets in Gaza, including a mosque, a day after a senior Hamas leader and his family were killed in an air strike.
Palestinian militants have also fired more rockets into Israel, Israel says.
Four Israelis have been killed so far by militant rocket fire.
Source: BBC NEWS