Israel imposes total siege on Gaza after Hamas surprise attack

Israel imposed a total siege on the Gaza Strip Monday and cut off the water supply as it kept bombing targets in the Palestinian enclave in response to the Hamas surprise assault it has likened to the 9/11 attacks.

Reeling from the Islamist group's unprecedented ground, air and sea attacks, Israel has counted over 700 dead and launched a withering barrage of strikes on Gaza that have killed 560 people there.

The skies over Gaza were blackened by plumes of smoke from deafening explosions as Hamas kept launching rockets as far as Tel Aviv and Jerusalem, where missile defence systems fired and air raid sirens blared.

Hamas -- whose militants surged into Israeli towns on Saturday, sprayed gunfire at civilians and dragged off about 100 hostages -- claimed on Monday that Israeli air strikes had killed four of the captives.

Israel said it had called up 300,000 army reservists, and truck convoys were seen moving tanks to the south, where its forces had dislodged the last holdout Hamas fighters from embattled towns.

"We are in control of the communities," said military spokesman Daniel Hagari, cautioning that some "terrorists" may remain after about 1,000 militants swarmed into the region on the Jewish Sabbath.

Defence Minister Yoav Gallant said Israel would impose a "complete siege" on the long blockaded enclave and stressed what this meant for its 2.3 million people: "No electricity, no food, no water, no gas -- it's all closed."

Palestinians in the impoverished coastal territory braced for what many feared will be a massive Israeli ground attack aiming to defeat Hamas and liberate the hostages.

Israel Prime Minister Benjamin Netanyahu has warned Gaza civilians to get away from all Hamas sites, which he vowed to turn "to rubble".

Middle East tensions have spiked as Israel's arch enemy Iran and their Lebanese ally Hezbollah have praised the Hamas attack, although Tehran rejected any role in the military operation.

Hamas has called on "resistance fighters" in the occupied West Bank and in Arab and Islamic nations to join its "Operation Al-Aqsa Flood", launched half a century after the 1973 Arab-Israel war.

The United States has pledged "rock solid" support for Israel and said it would send munitions and military hardware to its key ally and divert an aircraft carrier group to the eastern Mediterranean.

- 'Worst in Israeli history' -

Israel, which has long prided itself on a high-tech military and intelligence edge in its many conflicts, has been shaken to the core by Hamas's unprecedented attack.

It now faces the threat of a multi-front war after Hezbollah launched guided missiles and artillery shells from the north Sunday "in solidarity" with Hamas, in what some observers considered a warning shot.

Israel has voiced alarm and revulsion after more than 1,000 militants broke through the Gaza border fence Israel had deemed impregnable and swarmed out into nearby Jewish communities.

Among the hostages they took back into Gaza were children and a Holocaust survivor in a wheelchair, Israeli officials have said.

Up to 250 bodies were strewn across the site of a music festival in a Negev desert kibbutz, mostly young people, while other revellers were feared to be among the hostages.

"They butchered people in cold blood in an inconceivable way," said Moti Bukjin, a spokesman for the Zaka volunteer group which helped collect the bodies.

Israelis have voiced anger at the intelligence failure that blindsided the nation, but have attempted to put aside for now deep political divisions of recent years as they braced for what Netanyahu has warned would be a "long and difficult war".

"Never before have so many Israelis been killed by one single thing, let alone enemy activity in one day," said army spokesman Lieutenant Colonel Jonathan Conricus.

The multi-pronged attack had brought "by far the worst day in Israeli history", he said, likening it to a combination of the "9/11 and Pearl Harbour" attacks.

The situation was also dire inside Gaza, which has been blockaded by Israel since Hamas assumed control there 15 years ago, a period that has seen multiple wars with Israel.

Air strikes have levelled residential tower blocks, mosques and the central bank. More than 120,000 people in Gaza have been displaced, said the United Nations.

"The situation is unbearable," said Amal al-Sarsawi, 37, as she took shelter in a school classroom with her terrified children.

Children's sense of safety has been "ripped away" said Jason Lee of charity group Save the Children. "Our teams and their families are terrified, they feel like sitting targets.

"Children across the region are in constant fear."

- Global shock waves -

Palestinians in the occupied West Bank have rallied in support and clashed with Israeli security forces in violence that has killed 15 Palestinians since Saturday.

Anti-Israel activists have  demonstrated in Iraq, Pakistan, the United States and other countries, while security was stepped up around Jewish temples and school worldwide.

The spiralling conflict has sent shock waves around the world amid fears of a wider escalation, sparking a surge in oil prices on fears of tightening supplies.

Western capitals have condemned the attack by Hamas, which the United States and European Union consider a terrorist group.

Foreign or dual nationals have been reported killed, abducted or missing by countries including Brazil, Britain, Cambodia, Canada, France, Germany, Ireland, Mexico, Nepal, Panama, Paraguay, Thailand, Ukraine and the United States.

In the Egyptian city of Alexandria a police officer opened fire "at random" on Israeli tourists Sunday, killing two of them and their Egyptian guide before he was arrested.

Israel, which has struck a series of US-brokered normalisation deals with several Arab nations in recent years, has issued a travel warning for its citizens, especially in the Middle East.