"I call on the Israeli authorities to respect their international obligations and ensure a 'humanitarian space' for the delivery of vital relief," he said.
In the occupied West Bank, where Palestinians rallied for a third day of protests, Israeli soldiers shot and killed a man, Palestinian medical sources said.
Mufid Saleh Walweel, 22, was shot in the head in the West Bank city of Qalqilya during a protest against Israel's military operation in the Gaza Strip, they said.
There were also protests in Turkey, where organisers claimed 700,000 people had turned out for an anti-Israeli demonstration.
Protesters called on Turkey, Israel's only Muslim ally, to re-evaluate ties with the Jewish state if it does not halt its incursion in the Gaza Strip.
In Greece, demonstrators set fire to banks, threw rocks and fired flares at police in the capital Athens.
In Morocco, a crowd of 40,000 gathered in Rabat to condemn "the silence of Arab regimes".
Mustapha Ramid of the Islamist Party of Justice and Development, said "the blood of Gazan martyrs has mobilised the masses in Morocco and throughout the rest of the Arab world".
Several countries have called on Israel to exercise restraint as the civilian death toll continues to rise.
Russia on Sunday said it was "extremely concerned" by Israel's land operation in Gaza and said it was sending a special envoy to the region to help bring about a ceasefire by both sides.
Thousands of demonstrators in Indonesia, the world's most populous Muslim nation, denounced Israel as a "terrorist" force and called on the government to send troops to fight Israeli forces.
"Indonesia's military must go to war against Israel, not just as peacekeepers. We ask the government to send troops there, not just medicine," Farid Wadjdi, the local head of the Hizbut Tahrir movement, was quoted as saying by news website Detikcom.
Iran, which has seen angry protests since the Israeli raids began last week, also added its voice.
Ali Larijani, the parliament speaker, praised Palestinian resistance against the ground invasion.
"Zionists should know that Gaza will become their cemetery," he said on Sunday.
Even Egypt, which has faced criticism from the Arab and Muslim world, condemned the Israeli incursion, and called on the UN to work to end the violence.
|Shoes litter Whitehall in London in protest against Israel [AFP]
In Britain, where one of the world's largest demonstrations against the Israeli incursion took place on Saturday, Gordon Brown, the prime minister, took a more measured approach, saying that Israel's ground offensive had created a "very dangerous moment" before calling for increased efforts on both sides to secure a ceasefire.
"First we need an immediate ceasefire, and that includes a stopping of the rockets into Israel. Secondly, we need some resolution of the problem over arms trafficking into Gaza and, thirdly, we need the borders and the crossings open and that will need some international solution."
For its part, the US state department said it told the Israeli government that any military action should be "mindful of the potential consequences to civilians".
It also condemned Hamas, saying the group was holding the people of Gaza "hostage" and contributing to a "very bad daily life" for the coastal territory's residents.