The World Health Organisation (WHO) is calling for a humanitarian corridor to supply civilians in the Gaza strip with basic necessities, saying its supplies in the territory had been exhausted.
Hospitals would be unable to cope with the high number of wounded without further support, a WHO spokesman warned in Geneva.
He said that by Monday afternoon, 13 clinics in the densely populated Palestinian territory had come under fire from Israel retaliatory airstrikes.
He added that under international humanitarian law health facilities must be protected from attacks.
Six medical workers have been killed in Gaza and four wounded, he said.
According to Israel, one paramedic was killed in Israel in the multi-pronged attacks launched by Palestinian militants at the weekend.