The UN's senior human rights official says Israel's air campaign in Gaza could violate international laws prohibiting the targeting of civilians.

Navi Pillay said the Israeli military, which claims to have hit more than 1,100 targets it says are mostly rocket-launching sites, and the Gaza militants, who have fired more than 550 rockets against Israel, must abide by international law.

Ms Pillay said in a statement she has "serious doubt about whether the Israeli strikes have been in accordance with international humanitarian law and international human rights law".

She said civilians "are bearing the brunt of the conflict" between Israel, Hamas and Palestinian armed groups in Gaza, and called on all sides to refrain from launching attacks or putting military weapons in densely populated areas.

Ms Pillay said: "We have received deeply disturbing reports that many of the civilian casualties, including of children, occurred as a result of strikes on homes. Such reports raise serious doubt about whether the Israeli strikes have been in accordance with international humanitarian law and international human rights law."

She said she had seen for herself in Gaza how traumatic the air strikes and rocket attacks are for civilians, particularly children. Her office said civilians bear the brunt of the conflict and all sides must refrain from launching attacks or putting military weapons in densely populated areas.

"Israel, Hamas, and Palestinian armed groups in Gaza have been down this road before, and it has led only to death, destruction, distrust and a painful prolongation of the conflict," Ms Pillay said.

Targeting civilian homes violates international humanitarian law, but not if the homes are used for military purposes. But even then attacks on a home used by a military must be proportionate.