Jordanian protesters shout anti-Israeli slogans and wave Arabic and Hamas banners during a demonstration Saturday in Amman, Jordan. (Mohammad abu Ghosh/Associated Press)

International reaction to Israeli air strikes on the Gaza Strip was swift Saturday, with many around the world calling on both sides to halt attacks and end the violence that has left more than 225 people dead in less than 24 hours.

Leaders in the U.S., U.K., Canada and in the Middle East, as well as at the Vatican and the United Nations, have all called for an immediate restoration of calm.

"The [UN] Secretary-General is deeply alarmed by today's heavy violence and bloodshed in Gaza, and the continuation of violence in southern Israel," United Nations Secretary General Ban Ki-moon said in a statement.

The secretary general condemned Israel's air strikes, which were launched at various targets in Gaza just before noon, as an "excessive use of force." Hamas officials have said all of its security compounds were destroyed in the blasts, while Israel Army Radio reported 40 targets hit.

Ki-moon also implored Gaza militants to end several days of rocket attacks on Israeli towns and communities.

Rocket attacks

Israel's offensive against the Palestinian territory, spurred by dozens of rocket attacks on Israeli targets this week, has resulted in some of the worst destruction the region has seen in years. It comes after a six-month ceasefire between Israel and Gaza militants ended eight days ago.

At least 400 people were wounded in Saturday's attacks, most of whom were security officers although an unknown number of civilians are also amongst the dead.

Hamas has retaliated with up to 70 rocket attacks on Israeli border communities, and is threatening to resume suicide attacks.

The United States has blamed Hamas, the Islamist political and military organization that holds de facto control of Gaza, for breaking the ceasefire, saying it was "completely unacceptable" for militants to launch attacks on Israel after the sustained truce.

"The United States strongly condemns the repeated rocket and mortar attacks against Israel and holds Hamas responsible for breaking the ceasefire and for the renewal of violence in Gaza," Secretary of State Condoleezza Rice said in a statement.

Canada defends Israeli action

Canada's foreign affairs minister, Lawrence Cannon, also issued a statement in which he pointed to Israel's "clear right to defend itself" against continuing attacks by militants he accused of "deliberately" targeting civilians.

"First and foremost, those rocket attacks must stop. At the same time, we urge both sides to use all efforts to avoid civilian casualties and to create the conditions to allow safe and unhindered humanitarian access to those in need in Gaza."

Israeli police officers scuffle with Israeli activists during a Tel Aviv protest against the Israeli strikes on the Gaza Strip on Saturday. (Ariel Schalit/Associated Press)

Cannon also urged renewed efforts to reach a truce. While the ceasefire brought some calm to the coastal area around Gaza and saw fewer rocket attacks on southern Israeli towns, both Israel and Hamas have accused one another of violating the terms of the agreement.

The 22-member Arab League has scheduled an emergency meeting Sunday to discuss the situation, which has sparked angry protests throughout the Arab world.

Palestinian President Mahmoud Abbas, a senior member of Hamas's rival Fatah party and ruler of the West Bank, condemned Israel's actions.

Speaking from Riyadh, Abbas said "there are no reasons for the Israeli raids," according to Britain's Press Association.

Neighbouring Egypt, which helped broker the ceasefire in June, has summoned the Israeli ambassador to express condemnation and opened its Rafah border crossing to allow ambulances to bring the wounded to Egyptian medical facilities.

Egypt blames Israel

In a statement issued Saturday, the Egyptian presidency said it holds Israel responsible for the casualties in Gaza, according to Reuters.

"Egypt will continue its contacts to prepare an atmosphere conducive to restoring the period of calm and achieving reconciliation between the Palestinian groups," it said.

Protests against the Israeli offensive were staged across the Palestinian territories of the West Bank and Hebron on Saturday, as well as in neighbouring Jordan, Lebanon, Egypt and in Pakistan.

Elsewhere, Palestinian-Canadians called on the Canadian government to pressure Israel to end its offensive — even as a senior Israeli military source said the campaign against Hamas in the Gaza Strip "may last for a long time" and even expand to the use of ground forces.

Farid Ayad, a Toronto-area community leader who represents about 12,000 Palestinian-Canadians under the organization Palestine House, called the strikes "outrageous" and characterized them as an act of "genocide."

With files from the Canadian and Associated Press