GAZA CITY, Gaza Strip (AP):

Israeli warplanes pounded the homes of Hamas leaders and ground troops edged closer to the Gaza Strip's densely populated urban center yesterday, as Israel weighed a decision to escalate its devastating offensive.

Despite the tightening Israeli cordon, militants managed to fire off at least 15 rockets yesterday. There were no reports of injuries, though one rocket hit a house in the southern city of Ashkelon.

A few hours after that strike, Israeli Prime Minister Ehud Olmert visited Ashkelon and said Israel would end the conflict if rocket fire on Israel stops and Hamas is unable to re-arm.

"Anything else will be met with the Israeli people's iron fist," Olmert said. "We will continue as long as necessary to remove this threat from our heads."

Black smoke rose over Gaza City's suburbs, where the two sides skirmished throughout the night. At least 16 Palestinians were killed yesterday, Gaza health officials said. One of the dead was a militant killed in a northern Gaza battle.

Use of reserves

The army announced Sunday that it was sending reserve units into Gaza to assist thousands of ground forces already in the territory. The use of reserves is a strong signal that Israel is planning to move the offensive, which Gaza officials say has killed some 910 Palestinians, into a new, more punishing phase.

Israel launched the offensive on December 27, bombarding Gaza with dozens of airstrikes before sending in ground forces a week later. The operation is meant to halt years of Palestinian rocket attacks on southern Israel. Fighting has persisted despite international calls for a cease-fire. Thirteen Israelis, including 10 soldiers, have died.

Egypt, which often serves as a mediator between Israel and Hamas, has been playing a key role in trying to forge a cease-fire.

Egypt is critical to both sides because Hamas smuggles weapons under the Gaza-Egyptian border, and Israel wants those routes sealed as part of any peace deal.