"All sides must halt fire immediately," Ban said, as an Israeli military operation against rocket-firing militants in Gaza entered a sixth day, with 109 Palestinians and three Israelis killed.
"Further escalating the situation will put the entire region at risk," he added, sitting alongside Arab League chief Nabil al-Arabi after the two had held what Ban described as a "very constructive meeting."
"I`m visiting the region because of the alarming situation in Gaza," the UN secretary general said. "I`m here to appeal personally for an end to the violence."
He and Arabi, he said, "share a deep concern about the appalling rising cost in human lives" in Gaza.
An Israeli ground offensive in Gaza, Ban said, "would only result in further tragedy."
"Once again families and children are dying as a result of senseless violence," said Ban, who arrived in Cairo on Monday to bolster Egypt-brokered efforts for a ceasefire in Gaza.
The UN chief was later Tuesday to fly to Israel for meetings with Israeli Prime Minister Benjamin Netanyahu and Palestinian president Mahmud Abbas.
Egyptian mediators have been hosting marathon indirect talks between a Hamas team led by Khaled Meshaal and an Israeli envoy, which an Egyptian official said had produced "encouraging signs" on ending the crisis.
"The secretary general wishes to add his diplomatic weight to these efforts, which are considerable and extremely important," UN spokesman Martin Nesirky told reporters from Cairo on Ban`s arrival.