Thousands of people have attended the funeral of seven members of a Palestinian family killed in an explosion on a Gaza beach on Friday.
Many mourners were in tears as the procession poured through the town
There were emotional scenes as the bodies of a husband, wife, four daughters and a son were carried to the cemetery in the town of Beit Lahiya.
Palestinian militant group Hamas accuses Israel of killing the family.
Hamas said it fired rockets at Israel for the first time since its truce 16 months ago, in response to the deaths.
There were no Israeli reports of damage from the rockets, but one reportedly fell on Jabaliya refugee camp in northern Gaza.
In a separate incident, the vehicle of senior Gaza security official Rashid Abu Shbak was caught in a gunbattle between police and Hamas gunmen at a security officer's funeral.
Israel, which has been shelling open areas of northern Gaza to prevent rocket attacks, promised to investigate the deaths.
"If innocent civilians have been killed by an Israeli shell, that is totally unacceptable," said government spokesman Mark Regev.
"If people have to pay a price with their careers because of negligence or some other factor, that will be done ..."
Thousands gathered for the funeral at Beit Lahiya's central mosque with many praying outside because of overcrowding.
Later mourners surged down the main street carrying the dead wrapped in white shrouds and green Islamic flags.
Armed men fired into the air in salute and others called for revenge over loudspeakers.
At the cemetery, seven-year-old Huda Ghalia, the last surviving family member, asked for forgiveness as she bent down to kiss her father's face.
Huda, who was asleep under a blanket when the explosion occurred, has been symbolically adopted by Palestinian leader Mahmoud Abbas and Prime Minister Ismail Haniya.
There has been further criticism of Israel. Jordan spoke of the killings as a crime which would further increase tensions, while Turkey said they were a severe blow to efforts to bring peace.
Five Israeli human rights organisations demanded an urgent to end the killing of Palestinian civilians by Israeli security forces.
A joint statement put out by the organisations says that since October 2000 at least 1,647 Palestinians - nearly half the number killed by Israeli troops - had been taking no part in fighting at the time of their deaths.
The groups said 704 under-18s had been killed by Israeli troops and blamed "illegal expansion of Israel's open-fire regulations, double messages regarding the use of force... and failure to conduct independent investigations".
Government spokesman Ghazi Hamad told the BBC that Friday's deaths had changed what he called "the rules of the game", and that Hamas suicide attacks could resume.
Palestinian PM Ismail Haniya visited the wounded in hospital
A spokesman for Hamas's armed wing, the Izzedine al-Qassam brigade, said in the future rockets would be longer range and hit deeper inside Israel.
Under the ceasefire arrangement agreed with Palestinian Authority President Mahmoud Abbas, Hamas enjoyed enormous political success, taking power with a landslide victory in parliamentary elections in January.
So far this does not amount to a complete change in Hamas's position but if it were to return to widespread militant activity, the question would be how Israel might respond, our correspondent adds.
In the past, it has refused to differentiate between political and armed wings, assassinating a number of Hamas leaders, including its founder, Sheikh Ahmed Yassin.