Anti-Israel demonstrations were held in many countries and there was an immediate fallout with the suspension of efforts to hold talks between Syria and Israel.
International powers renewed calls for a ceasefire, but US President George W. Bush and president-elect Barack Obama maintained their silence on the fighting.
Thousands of Iranians, who were joined by high ranking Iranian officials and military commanders, shouted 'Down With USA' and 'Down With Israel' in Tehran on Monday. Many carried banners reading 'Israel must be wiped off the face of the earth' and 'We should all rise and destroy Israel.'
Iran's supreme leader Ayatollah Ali Khamenei on Sunday urged Muslim states to punish Israel and deplored what he said was silence by some Arab leaders over the attacks. Tehran is a staunch supporter of Hamas but rejects allegations that it supplies arms to the movement.
Demonstrators have been held around the world since the Israeli offensive started Saturday. Arrests were made during demonstrations in European capitals on Sunday, including 10 in London.
About 8,000 people staged a rally in the southern Egyptian city of Assiut on Sunday, while several thousand attended rallies in the capital Cairo and the port city of Alexandria, a security official said.
In Turkey, thousands of people joined demonstrations in about a dozen cities. Egyptian Foreign Minister Ahmed Abul Gheit arrived in Ankara on Monday for talks with Turkish leaders on the Israeli offensive, a foreign ministry official said.
Turkish Foreign Minister Ali Babacan said Turkish-mediated indirect peace talks between Israel and Syria have become 'impossible' after the Israeli offensive.
'To make war on the Israeli-Palestinian track and at the same time make peace on the Israeli-Syrian track - these two cannot go together,' he said.
In Syria, protesters burned Israeli and American flags as thousands demonstrated in Damascus on Sunday. There were similar scenes in the Jordanian capital Amman where hundreds gathered to demand the closure of the Israeli embassy.
Saudi Arabia sent two hospital aircraft with medical personnel to Gaza to help with the injured and to fly any severely injured to hospitals in Saudi Arabia, the government said.
Indonesia, the world's most populous Muslim nation, also offered medical aid and joined Pakistan, Afghanistan, Malaysia and other Muslim nations in condemning Israel.
There were new calls for a halt to the fighting which erupted after the breakdown of a truce between Israel and Hamas.
UN Secretary General Ban Ki-moon 'deplores that violence is continuing today, and he strongly urges once again an immediate stop to all acts of violence,' his spokeswoman Michele Montas said in a statement issued late Sunday.
The UN Security Council issued a non-binding statement calling for 'an immediate halt to all violence' in the Gaza Strip where Israeli air strikes went on for a third day while Israeli tanks were massed on the border.
China expressed major concern.
'The Chinese side is shocked and seriously concerned over the current military operations in Gaza that have caused a large number of deaths and injuries,' Vice Premier Li Keqiang said in a statement.
European nations called for a ceasefire. Many foreign ministers have spoken to Israel's Foreign Minister Tzipi Livni British Foreign Secretary David Miliband warned the Middle East was facing a 'dangerous and dark moment' as he renewed a call for an end to the fighting.
Mr Miliband told BBC radio: 'I think that any innocent loss of life is unacceptable and in this case there have been massive casualties, some of them civilians and some of them children.
Russian Foreign Minister Sergei Lavrov who also spoke to Livni made a call to 'urgently halt' the military action.
A top aide to Barack Obama said the US president-elect was committed to achieving peace in the Middle East.
Recognising the special relationship between the United States and Israel, Obama would work closely with the Israelis, Mr David Axelrod told CBS television that the new US leader 'will do so in a way that will promote the cause of peace, and work closely with the Israelis and the Palestinians on that - toward that objective.'
The outgoing Bush administration blamed Hamas 'thugs' for provoking the offensive by firing rockets into Israel from Gaza. -- AFP