A Palestinian boy injured in an Israeli attack is carried into the emergency room at Shifa hospital in Gaza City on Saturday. (Ashraf Amra/Associated Press)Israeli planes dropped leaflets into the Gaza Strip on Saturday, warning residents of an escalation in attacks, while the exiled leader of Hamas said his group won't consider a ceasefire until Israel ends its offensive and opens the Palestinian territory's border crossings.

In a fiery speech broadcast on the Arabic news channel Al-Jazeera, Khaled Mashaal labelled Israel's military offensive in Gaza a "holocaust," saying it has killed the last chance for settlement and negotiations with Israel.

Members of an Israeli family show fear as they walk along a street after a rocket fired by Palestinian militants from the Gaza Strip hit the southern Israeli city of Ashkelon on Saturday. (Tsafrir Abayov/Associated Press)"Let Israel pull out first, let the aggression stop first, let the crossings open and then people can look into the issue of calm," Mashaal said during the broadcast from the Syrian capital, Damascus.

Mashaal's comments came as Hamas teams were in Cairo to negotiate over an Egyptian-proposed ceasefire.

At least 30 Palestinians killed on Saturday: medics

On the 15th day of the offensive against Hamas targets, the Israeli military launched dozens of air strikes aimed at rocket-launching sites and smuggling tunnels, while Gaza medics said more than 30 Palestinians, many of them non-combatants, were killed in the day's attacks.

In the day's bloodiest incident, an Israeli tank shell killed nine people in a garden outside a home in the northern Gaza town of Jebaliya, said Adham el-Hakim, administrator of Kamal Adwan hospital. The nine were from the same clan and included two children and two women.

However, the Israeli military said its forces did not carry out attacks in that area on Saturday.

Saturday's attacks came after more than 15 militants were killed in overnight fighting, the Israeli military said earlier in the day.

The Israeli leaflets urged Gaza residents not to help Hamas, the Islamist militant group that rules Gaza, and to stay away from its members.

"The IDF (Israeli Defence Forces) will escalate the operation in the Gaza Strip," the leaflets said in Arabic. "The IDF is not working against the people of Gaza but against Hamas and the terrorists only. Stay safe by following our orders."

It is widely believed that the next phase of the operation calls for Israeli troops to move closer to or enter Gaza's cities and refugee camps, which could lead to higher casualties on both sides.

The Israeli military also promised to hold fire for three hours Saturday to allow humanitarian aid through. But for the second straight day, fighting continued even during the lull.

Palestinian death toll 821

Palestinians walk in front of a building destroyed by an Israeli air strike in Gaza City on Saturday. (Hatem Moussa/Associated Press)The Hamas-run health ministry in Gaza said 821 Palestinians have died in the offensive. Thirteen Israelis, including 10 soldiers and three civilians, have been killed, Israeli officials say.

At least 10 Hamas rockets landed in Israel on Saturday, the army said. One rocket hit an apartment building in the southern city of Ashkelon, lightly wounding two people and causing extensive damage.

Neither side in the conflict has accepted the UN Security Council resolution, adopted Thursday, that called for a ceasefire.

The United Nations suspended relief deliveries in Gaza on the same day, citing Israeli attacks on its facilities and personnel. On Friday, the UN Relief and Works Agency said its aid would flow again only after a ceasefire comes into effect.

Aid groups have said the short lulls in fighting over the past four days haven't given them enough time to do their work.

The Israeli military, meanwhile, denied Saturday that Israeli soldiers had shot at a UN aid truck in a convoy headed to a Gaza crossing two days ago.

Truck drivers at the scene told UNRWA that they saw an Israeli tank nearby after they were fired upon. However, an Israeli military source told the Reuters news agency that Israel suspects Hamas was behind the shooting.

Israel launched an air offensive Dec. 27 to halt Palestinian rocket attacks on southern Israel. A week later, troops and tanks moved in. They remain on the periphery of Gaza City.

With files from the Associated Press