UN High Commissioner for Human Rights Navi Pillay denounced the Israeli raids on Gaza as "deeply disturbing" and a violation of international law.
"We have received deeply disturbing reports that many of the civilian casualties, including of children, occurred as a result of strikes on homes," Pillay said. "Such reports raise serious doubt about whether the Israeli strikes have been in accordance with international humanitarian law and international human rights law."
Furthermore, UN spokeswoman Ravina Shamdasani criticised the striking of homes as military targets, saying: "Even when a home is identified as being used for military purposes, any attack must be proportionate… and precautions must be taken to protect civilians."
Death toll in Gaza rose to at least 106 people on Saturday, as Israel continued its offensive for the fourth consecutive day, according to Gaza's Health Ministry. At least 75 of those killed are civilians, including 23 children, Reuters said.
Pillay also said the "indiscriminate firing of rockets from Gaza" could also be considered a breach.
"Every alleged breach of international law must be promptly, independently, thoroughly and effectively investigated, with a view to ensuring justice and reparations for the victims," she said.
"Israel, Hamas and Palestinian armed groups in Gaza have been down this road before, and it has led only to death … and a painful prolongation of the conflict," Pillay added.
She added that Palestinians fired more than 800 rockets and 61 mortars on southern Israel, which led to the injury of nine Israeli civilians as they tried to escape to shelters, according to unconfirmed reports.
Jens Laerke, spokesman of the UN Office for the Co-ordination of Humanitarian Affairs (OCHA), said on Friday that more than 340 housing units in Gaza had been severely damaged or completely destroyed. "As a result, more than 2,000 people have been displaced," he said.