It struck a building close to the main gate of Shifa hospital in Gaza City, causing casualties, Palestinian police and medics said.

Moments later, a doctor at the city's main hospital said seven children had been killed while playing in a playground in a Gaza City refugee camp by a separate Israeli missile.

A Palestinian official said 10 people in total were killed in the strike on a park.

The attacks came less than an hour after UN Secretary-General Ban Ki-moon likened the conflict to a "manmade hurricane", saying "whole neighborhoods have been reduced to rubble".

He said Gaza was in a "critical condition" following Israeli strikes resulting in the deaths of hundreds of Palestian civilians, which raised "serious questions about proportionality".

Statistics published by OCHA, the UN humanitarian agency, show that some 22 hospitals, clinics and medical centres have been hit and damaged by Israeli shelling since the devastating military aggression began on July 8.

In a statement issued shortly before the strike, the World Health Organisation said it was "appalled" by the number of Israeli strikes on healthcare facilities and personnel.

"The World Health Organisation has been appalled by the continuing trend for healthcare facilities, staff and vehicles to come under direct fire in Gaza since the escalation of violence on 8 July 2014," a statement from the Geneva-based body said.

"It is vital for health facilities and staff to be able to perform their life-saving work without fear of attack," it said.

RA/NJF