UN says total siege of Gaza 'prohibited' under international law

Israel's total siege of the Gaza Strip, depriving civilians of goods essential for survival, is banned under international law, the United Nations human rights chief said on Tuesday.

Volker Turk, the UN high commissioner for human rights, said people's dignity and lives had to be respected as he called for all sides to defuse the "explosive powder-keg situation".

Palestinian militant group Hamas, which abducted about 150 people in its surprise weekend assault on Israel, threatened to execute the hostages if Israeli air strikes continue "targeting" Gaza residents without warning.

The threat came after Israel on Monday imposed a total siege on the Gaza Strip, cutting off food, water and electricity supplies, and sparking fears of an increasingly desperate humanitarian situation.

"International humanitarian law is clear: the obligation to take constant care to spare the civilian population and civilian objects remains applicable throughout the attacks," Turk said in a statement.

The siege risk seriously compounding the already dire human rights and humanitarian situation in Gaza, including the capacity of medical facilities to operate, especially in light of increasing numbers of injured, the statement said.

"The imposition of sieges that endanger the lives of civilians by depriving them of goods essential for their survival is prohibited under international humanitarian law," Turk said.

Any restrictions on the movement of people and goods to implement a siege must be justified by military necessity or may otherwise amount to collective punishment, the statement added.

Khamenei denies involvement in attack on Israel

Supreme leader Ayatollah Ali Khamenei on Tuesday denied any Iranian involvement in Hamas's shock weekend attack on Israel despite its strong support for the Palestinian militant group.

"The supporters of the Zionist regime (Israel) and some people in the usurping regime have been spreading rumours over the past two or three days, including that Islamic Iran was behind this action. They are wrong," Khamenei said in a speech at a military academy.

"Of course, we defend Palestine, we defend the struggles," he added, urging "the whole Islamic world" to "support the Palestinians."

Khamenei said Israel has suffered an "irreparable failure" on both "military and intelligence" fronts.

"Everyone has spoken of the failure, I put the emphasise on its irreparability," he said.

Iran took the lead on Saturday in celebrating the Hamas assault in which at least 1,500 gunmen stormed the border before carrying out a bloody rampage through Israeli communities that left more than 900 dead.

The Israeli army said it was the single deadliest event in the nation's history, and has responded with a ferocious bombardment of Gaza where officials say at least 687 people have been killed.