UN humanitarian undersecretary Valerie Amos has demanded a halt to the violence in Gaza, saying "so many children" are among the more than 700 Palestinians killed. Israel says the toll among its troops has risen to 32.
Top diplomats of the US, Britain and the UN pressed on with bids to get a ceasefire between Israel and Hamas militants on Thursday after 21 more Palestinians were killed in a night of Israeli airstrikes and shelling.
From exile in Qatar, Hamas leader Khaled Meshal rejected any truce without the lifting of Israel's eight-year blockade on Gaza.
Palestinian medics quoted by the news agency AFP said the 21 killed, including a family of six, took the total number of Palestinian casualties in 17 days of bloodshed to 718.
The Israeli army said its troop losses had risen to 32 with the deaths of three more soldiers killed in combat inside Gaza on Wednesday.
A Thai farm laborer had also died when a rocket fired from Gaza struck a greenhouse in southern Israel.
'Terrible situation,' says Amos
The UN's undersecretary for humanitarian affairs and emergency relief, Valerie Amos, speaking from a UN meeting in Tokyo described Gaza as a "terrible, terrible situation," adding that "so many children have been killed as a result of the violence in the last few days."
Figures provided by the United Nations classified 74 percent of those killed as civilians, of which more than 120 were children.
Aid groups said the situation in the small enclave was worsening, with water, sewage and power systems damaged and food reserves dwindling.
The news agency AFP said hundreds of people, mostly women and children, had packed into the Greek Orthodox church of Saint Porphyrios to shelter from the violence.
Diplomacy in search of cease-fire
Israeli Prime Minister Benjamin Netanyahu, who blames civilian casualties on the tactics of Hamas fighters, was visited by US Secretary of State John Kerry for two hours. Neither made subsequent statements.
Kerry left for Cairo to further discuss an Egyptian ceasefire proposal while Netanyahu met with his security cabinet.
Kerry held talks in Jerusalem with visiting UN chief Ban Ki-Moon, with both saying they were pooling their efforts to clinch a truce. Kerry also meet Palestinian President Mahmud Abbas in Ramallah while Ban reportedly had talks with Saudi King Abdullah in Jeddah.
The diplomatic flurry was joined by Britain's new Foreign Secretary Philip Hammond who held late-night talks with Abbas.
Hammond said beyond a ceasefire the region needed a "stable solution" for Palestinians and Israelis to live in peace together.
Israel preparing for 'next stages'
Israeli Defense Minister Moshe Yaalon said troops were "preparing for the next stages of the fighting" after uncovering and destroying a network of tunnels used by Palestinian militants along Gaza's border with Israel.
Early on Thursday, the US Federal Aviation Administration (FAA) said it was lifting its ban on flights to Tel Aviv imposed Tuesday, because of rocket salvos from Gaza.
But many other global airlines continued to avoid Israel. Israeli carriers continued to operate.
ipj/msh (AFP, Reuters, dpa, AP)