Hamas executed 18 alleged collaborators in Gaza City on Friday as Israeli Prime Minister Benjamin Netanyahu vowed harsh retribution for the killing of a four-year-old boy by Palestinian mortar fire.
The escalating bloodshed has seen another 76 Palestinians die in Gaza and wounded nine Israeli civilians since hostilities resumed on Tuesday after the collapse of truce talks and nine days of calm.
European governments are now seeking UN action to find a durable ceasefire after Egyptian diplomacy failed to end the worst fighting in the Israeli-Palestinian conflict since a 2000-2005 second intifada.
Israel has vowed no let-up until it can guarantee the safety of its civilians, and Hamas insists that Israel end an eight-year blockade on the tiny, over-populated Palestinian coastal enclave it controls.
At least 2,092 Palestinians have been killed since July 8, of whom the United Nations has identified 70 percent as civilians, and 68 people have died on the Israeli side, all but four of them soldiers.
In broad daylight outside Gaza's largest mosque, a day after Israel assassinated three of the movement's senior commanders, Hamas gunmen grabbed six men as worshippers came out onto the street after Friday prayers, witnesses told AFP.
They were pushed to the ground. One masked man shouted: "This is the final moment of the Zionist enemy collaborators," before the gunmen sprayed them with bullets.
Earlier, another witness saw 11 people shot dead in a square near the remains of Gaza police headquarters, bombed by Israeli warplanes.
An 18th person was shot in front of bystanders in a separate incident.
The Hamas-linked website Majd said the 11 were killed after they "gave information to the Zionist enemy".
- Israeli child killed -
International human rights organisations condemned the executions.
In Israel, the barrage of Palestinian rockets and mortar fire claimed its fourth civilian victim of the six-week war -- a boy killed at home after shrapnel pierced the wall in a southern community.
Police said the boy was four years old, making him the first Israeli child killed by Palestinian fire since July 8.
"Hamas will pay a heavy price for this attack," Netanyahu's spokesman Ofir Gendelman quoted the premier as saying on his Twitter account.
The army and Shin Bet internal security would "intensify ops against Hamas", he added.
Israel said it struck more than 30 targets in Gaza since midnight as upwards of 70 rockets and mortar rounds hit Israel during the same period.
Another nine rockets were shot down, an army spokeswoman said.
Israeli air strikes on Friday killed five Palestinians in the Nusseirat refugee camp and the central town of Deir al-Balah, three of them men aged 22, 24 and 45.
Forty others were wounded when a powerful air strike levelled a house in Gaza City late Friday, emergency services said.
Witnesses said it was the home of a family that included members of Hamas, but that the family had evacuated the building beforehand.
- Abbas, Meshaal 'appeal to UN' -
The Palestinian president and Hamas's exiled leader Friday urged the United Nations to draw up a "timetable" for the Israeli occupation of Palestinian territories to end, Qatar state media said.
President Mahmud Abbas and Hamas supremo Khaled Meshaal issued the appeal during talks in Doha, as fighting continues in Gaza, Qatar's state news agency QNA said.
The two Palestinian leaders have been holding talks in Doha since Thursday, but little else has filtered out of their meetings which are hosted by the emir of Qatar, a key backer of Hamas.
On Thursday, Britain, France and Germany put forward key points of a new UN Security Council resolution calling for an immediate and sustainable ceasefire, and the lifting of Israel's blockade.
Diplomats said the text was aimed at advancing efforts to reach agreement within the 15-member council after a draft resolution from Jordan met with resistance, notably from the United States.
Washington has wielded its veto powers at the Security Council repeatedly in the past on behalf of Israel, although the now 46-day war has strained relations between the allies.
The new resolution proposes a mechanism to monitor the ceasefire and supervise the movement of goods into Gaza to allay Israeli security concerns.
It also calls for Abbas's Western-backed Palestinian Authority to take back control of Gaza, seven years after his loyalists were driven out of the territory by Hamas.
Iran, Israel's arch-enemy, also plans to send aid to Gaza after Egypt said it would allow the shipment to cross its border with the Palestinian territory, an Iranian diplomatic source said.
The official IRNA news agency said a first Iranian Red Crescent shipment of 100 tonnes of medicine and food would be flown "soon" to Cairo, citing a foreign ministry source in Tehran.