Gaza-fired rocket hits near Tel Aviv
"The Israelis must realise that this aggression is unacceptable and would only lead to instability in the region and would negatively and greatly impact the security of the region," Mr Mursi said.
The new conflict will be the biggest test yet of Mr Mursi's commitment to Egypt's 1979 peace treaty with Israel, which the West views as the bedrock of Middle East peace.
The Muslim Brotherhood, which brought Mr Mursi to power in an election after the downfall of autocrat Hosni Mubarak, has called for a 'Day of Rage' in Arab capitals tomorrow. The Brotherhood is seen as the spiritual mentors of Hamas.
The offensive began yesterday when a precision Israeli airstrike killed Hamas military mastermind Ahmed Al-Jaabari. Israel then began shelling the enclave from land, air and sea.
The 15 killed in Gaza included Jaabari and six Hamas fighters plus eight civilians, among them a pregnant woman with twins, an 11-month old boy and three infants, according to the enclave's health ministry. Medics reported at least 130 wounded.
At Jaabari's funeral today, supporters fired guns in the air celebrating news of the Israeli deaths, to chants for Jaabari of "You have won."
His corpse was borne through the streets wrapped in a bloodied white sheet. But senior Hamas figures were not in evidence, wary of Israel's warning they are in its crosshairs.
The Israeli army said 156 targets were hit in Gaza, 126 of them rocket launchers. It said 200 rockets had struck Israel since the start of the operation, 135 of them since midnight.
Israel's Iron Dome interceptor system has so far shot down more than 80 rockets headed for residential areas, the military said.
Expecting days or more of fighting and almost inevitable civilian casualties, Israeli warplanes dropped leaflets in Gaza telling residents to stay away from Hamas and other militants.
The United States condemned Hamas, shunned by the West as an obstacle to peace for its refusal to renounce violence and recognise Israel.
"There is no justification for the violence that Hamas and other terrorist organisations are employing against the people of Israel," said Mark Toner, deputy US state department spokesman.
The UN Security Council held an emergency meeting late last night, but took no action.
In France, foreign minister Laurent Fabious said: "It would be a catastrophe if there is an escalation in the region. Israel has the right to security but it won't achieve it through violence. The Palestinians also have the right to a state."
