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 today, as Israel stepped up the pressure ahead of deciding whether to escalate its devastating two-week offensive.

From downtown Gaza City, black smoke could be seen rising over the eastern suburbs where the two sides skirmished throughout the night. At least six Palestinians were killed in the new airstrikes or died from their wounds today, Gaza health officials said. One of the dead was a militant killed in a northern Gaza battle.

Despite the tightening Israeli cordon, however, militants still managed to fire off a rocket this morning which fell near the southern town of Kiryat Gat but caused no casualties, police said.

The army announced Sunday that it had begun 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 already has killed some 870 Palestinians, into a new, more punishing phase.

Israel launched the offensive on Dec. 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.