Israel's aircraft pounded Hamas targets in the Gaza Strip on Saturday and scattered leaflets warning of an escalation in attacks, but there was no sign that its forces had begun a major advance on the militant group's urban strongholds.

A senior Hamas commander and seven members of a Palestinian family were among those killed on the 15th day of Israel's thundering air and artillery assault, which also damaged a hospital. Palestinian militants fired 15 rockets into Israel, wounding three people.

Diplomatic efforts to end the fighting sputtered as Egypt rebuffed a proposal to place international forces along its border to help prevent weapons smuggling into Gaza. Israel says the offensive is aimed at stopping rocket fire from Gaza and will continue until weapons pipelines into the Hamas-ruled coastal enclave are cut off.

The warning of a "new phase" of the assault, which has killed more than 800 Palestinians, came in leaflets dropped over Gaza City and the southern town of Rafah and in automated calls to Palestinians' cellphones.

"The IDF [Israel Defense Forces] will escalate the operation in the Gaza Strip," the messages 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."

The leaflets urged residents not to help Hamas and to stay away from its members.

Israeli ground forces invaded Gaza a week ago, on the eighth day of airstrikes, and have moved to the outskirts of cities. Although there was no sign of an advance, the warnings heightened the panic that has gripped Gaza's 1.5 million people since the offensive began Dec. 27. Scores of families were seen loading mattresses and other belongings into and atop their cars and moving from outlying neighborhoods of Gaza City to places of refuge closer to the center.

In the day's bloodiest incident, seven members of the Abed Rabbo clan were killed in the late-morning shelling of their grocery store in a village, just east of the Jabaliya refugee camp, that bears the family's name.

Ziad Barqouni, an ambulance driver, said neighbors told him that the shelling had come from an Israeli tank several blocks away. Barqouni said he saw an Israeli helicopter firing into the village as he approached.

The Israeli army denied attacking the area at the time.

Barqouni said he found four bodies on the floor of the store and three on the street outside. Six members of the family crowded into three ambulances that removed the bodies for burial in Jabaliya.

Abdel Haq Abed Rabbo rode in one ambulance, caressing the face of his dead wife, Randa, as he wept and cursed Israel. "This is a sin, a crime. God have mercy," he said over and over.

The couple's 21-year-old son, Sufian, and five of his cousins, ages 13 to 32, also died.

Twelve other Palestinian civilians were reported killed Saturday.

Families have been devastated by multiple losses as the Israeli military targets homes that it says are Hamas hide-outs or weapons storage sites.

On Saturday, relatives reported the deaths of Mohammed Ibrahim Quran, 58, two of his teenage children and four adult members of his extended family of fishermen in a series of airstrikes early Friday on his seaside home in Deir al Balah.

Abed Quran, a 41-year-old nephew of Mohammed, said Israeli helicopters fired at surviving family members as they tried to take the wounded to a hospital and at ambulances that arrived later. The seven dead and 21 wounded finally reached the hospital seven hours after the initial airstrike.

"They blindly targeted everything that moved," said another nephew, 17-year-old Jalal Quran.

The army said it was investigating the report.

Palestinian medical officials said Saturday that nearly half the 830 Gazans killed in the offensive were civilians. Israeli news media said the army estimated that it had killed 300 militants.

Thirteen Israelis have been killed: 10 soldiers, plus three civilians hit in Israel by rocket fire.

The army said its ground forces killed Amir Mansi, commander of Hamas' rocket-launching teams in Gaza City, after spotting him at a launch site there. Hamas confirmed his death.

With most Israeli ground forces holding their positions and Hamas eluding confrontation, the fighting has been relatively light in the last few days. Hamas has continued to fire rockets into Israel, but at a daily rate far below the recent peak of 80 launched on Christmas Day.

Saturday's heaviest encounters were reported along the coastal road north of Gaza City, where Israeli forces moved to within a mile of the city before pulling back slightly.

The army said 12 soldiers were wounded Saturday.

In Khan Yunis, an airstrike demolished part of a wall around the European Hospital, frightening patients and damaging underground fuel pipes and electrical cables.

"It shook the hospital," said Kamal Abu Mousa, the director. "The explosion was only [76 yards] from the main building and all our patients. The Israeli air force must have lost its mind."

The military said it was investigating the report.

Nisreen Mohammed Kurd, 19, said she was shaken by the blast and wanted to leave the hospital, where she is being treated for shrapnel wounds sustained during an airstrike. Her father, seated at her bedside, said no.

"There's no safe place in Gaza," he said.

Also Saturday, Human Rights Watch reported that its researchers had observed multiple air bursts of white phosphorous from Israeli artillery near Gaza City and Jabaliya on Friday and Saturday. The group said the army appeared to be using the smoke to conceal its operations, which is permissible under international law. But it urged Israel to refrain from using the substance, which can ignite houses and severely burn the skin, in Gaza's populated areas.

In response, the military insisted that it used only weapons permitted by international law but declined to disclose details about them.