GAZA CITY, Gaza Strip, (AP) – Israeli aircraft pounded Hamas weapons positions and Gaza smuggling tunnels, witnesses and the military said Wednesday, while militants in Lebanon raised the specter of a new front by sending three rockets crashing into northern Israel.

The rockets from Lebanon landed in open areas near the town of Kiryat Shemona, causing no injuries or damage, Israeli police said. Residents of northern Israel were instructed to head to bomb shelters following the second attack from Lebanon in less than a week.

U.N. Secretary General Ban Ki-moon was meeting with Egyptian President Hosni Mubarak in Cairo Wednesday in diplomatic efforts to end the violence in the Gaza Strip, which began 19 days ago. The Israeli air and ground offensive against the coastal territory’s Hamas rulers has killed more than 940 Palestinians, half of them civilians, according to Palestinian hospital officials.

Thirteen Israelis have also been killed, four of them by rocket fire from Gaza.

Eight years of Palestinian rocket attacks on southern Israeli towns sparked the war, which began on Dec. 27 with a devastating air offensive, then expanded to include a ground campaign.

There was no immediate claim of responsibility for Wednesday’s rocket attacks from Lebanon. Hezbollah, the Iranian-backed guerrilla group that fought a monthlong war with Israel in 2006, denied involvement in a similar attack last week and speculation has focused on small Palestinian groups in Lebanon.

The rockets flying across its northern border have fueled Israel’s fears that militants in Lebanon could try to open a second front in solidarity with Gaza’s Islamic militant Hamas rulers.

Lebanese security officials said the Israeli army fired shells on southern Lebanon in response. Israeli helicopter gunships flew reconnaissance missions along the heavily protected border as Lebanese troops and U.N. peacekeepers sent out patrols, the Lebanese officials said on condition of anonymity because they were not allowed to speak to the press.

The Israeli military confirmed that it returned fire, and said it regards the Lebanese government and military as responsible for preventing attacks on Israel.

Israeli military officials have said the cease-fire talks in Cairo, which they term “decisive,” will determine whether Israel moves closer to a truce or widens its offensive to send thousands of reservists into crowded, urban areas where casualties on both sides would likely mount.

Israel had planned to send its lead negotiator, Amos Gilad, to Cairo on Wednesday, but his trip was put off because conditions weren’t ripe, defense officials said. They spoke on condition of anonymity because the date of his departure has not been set.

Ban was meeting with Mubarak, who launched an initiative with France a week ago aimed at achieving a temporary halt to the fighting to be followed by a permanent cease-fire and arrangements on border security. He will head from Egypt to Jordan, Israel, the Palestinian-controlled West Bank, Turkey, Lebanon, Syria and Kuwait. His itinerary does not include a stop in Gaza, where Hamas is shunned by many world powers as a terrorist organization.

Israel pressed ahead with its military offensive overnight even as diplomatic efforts advanced. Warplanes and helicopter gunships pounded 60 targets overnight, including a police court in Gaza City, rocket-launching sites, weapons-production and storage facilities and about 35 weapons smuggling tunnels, the military said. Witnesses also reported an air strike on the house of a militant rocket squad leader.

A row of houses in Gaza City was demolished by a powerful air strike. The street was filled with rubble and furniture, severed electricity wires and telephone cables lay on the ground, and windows of nearby houses were shattered.

Four Palestinians, including at least two militants, were killed and 32 people were wounded in overnight fighting, Gaza hospital officials said.

Palestinians said aircraft also struck the Sheikh Radwan cemetery in Gaza City, destroying tombs and unearthing dozens of bodies. Gaza City residents, too terrified to venture out to the only area graveyard that has space for new graves, have reopened the Sheikh Radwan burial ground to bury their dead. The military had no immediate comment.

Early Wednesday, Israeli tanks resumed firing at civilian areas, using shells that ignited small fires before dissolving into clouds of white smoke that hung above the city center, witnesses said. The Israeli military has not confirmed allegations that it has improperly used white phosphorous shells, saying only that it uses munitions is in accordance with international law.

The International Committee of the Red Cross has urged Israel to exercise “extreme caution” in using the incendiary agent, which is used to illuminate targets at night or create a smoke screen for day attacks, said Peter Herby, the head of the organization’s mines-arms unit. The Red Cross said it had no evidence to suggest the incendiary agent was being used improperly or illegally.

Fireballs and smoke plumes from Israeli bombing have become a common sight in the territory of 1.4 million people, who are trapped because Israel and Egypt have blockaded border crossings ever since the Islamic militant Hamas group seized power in Gaza in June 2007.

Humanitarian concerns have increased amid the onslaught although some aid is getting through to Gaza during daily three-hour lulls Israel has allowed to let in supplies.

Palestinian rocket fire has dropped significantly since the offensive began. Twenty rockets and mortar shells were fired toward Israel on Tuesday, and there was no fire early Wednesday, the military said. In the early days of the offensive, militants fired as many as 80 a day.

Israel says it will push forward with the offensive until Hamas ends all rocket fire on southern Israel, and there are guarantees the militant group will stop smuggling weapons into Gaza through the porous Egyptian border.

Hamas has said it will only observe a cease-fire if Israel withdraws from Gaza.

Iranian state television reported Wednesday that the Israeli navy intercepted an Iranian ship loaded with medicine, food and clothing destined for Gaza, forcing the vessel to head toward an Egyptian port.

Ahmad Navabi, head of the humanitarian aid group sponsoring the ship, said on state television that the Israel navy approached the cargo ship just 20 miles off the coast of Gaza, and ordered it to turn around.

Meanwhile, Iran’s supreme political and religious authority, Ayatollah Ali Khamenei, has issued a religious opinion, or fatwa, urging Muslims throughout the world to avoid the purchase of any products that would profit Israelis.

The fatwa declares the purchase of any Israeli goods or trade with Israeli companies forbidden. Iran doesn’t recognize Israel and has no trade ties with the Jewish state but the ruling also affects international companies operating in Iran and outside Iran whose shareholders are Israelis.