“Military operations in populated areas inevitably cause civilian casualties, and in this operation several civilians have already been killed and wounded, including women and at least one Palestinian child,” Mr. Annan said in a statement issued by his spokesman.

“The Secretary-General urges Israel to exercise maximum restraint, do their utmost to protect civilians and to refrain from further escalating an already grave situation. He also calls on Palestinian militants to stop firing rockets against Israeli civilian targets,” the statement added.

“All concerned should remember that continuing violence is liable to make the search for a just and lasting peace in the region even more difficult.”

The UN Relief and Works Agency for Palestine Refugees (UNRWA) warned that the Israeli operation is taking place in an area densely populated by Palestinian refugees, with more than 10,000 students going to UNRWA schools and more than 400 Agency staff affected.

It said between 30 and 40 women today were collected inside two of its elementary schools, where their mobile phones were taken from them by Israeli soldiers. It confirmed that two of the women subsequently suffered gunshot wounds.

An ambulance was initially forbidden entry but the injured women have since been taken to Beit Hanoun hospital, it added.