London  - British Prime Minister Gordon Brown Tuesday urged "international engagement" to protect the security of Israel and create viable open borders for the Palestinians in Gaza in the wake of the current fighting.

Speaking to reporters in London, Brown described the escalating violence and the unfolding humanitarian crisis in Gaza as the "darkest moment yet for the Middle East," but also said that he was hopeful that a ceasefire could be reached.

"It's also because of the violence of war that we must work as hard as possible over the next few hours, and days if necessary, so that there is an immediate ceasefire," said Brown.

He said he had been discussing the situation with fellow world leaders, including from Egypt and Turkey, and had put forward proposals for making progress.

"I am hopeful that the basis on which an immediate ceasefire can take place can be found," Brown said, without specifying what the proposals were.

Any deal would have to involve an immediate ceasefire, including an end to rocket attacks by Hamas on Israel, an end to the smuggling of weapons through tunnels into the Gaza Strip as well as an "opening up of borders under international supervision."

Asked what form the international supervision should take, Brown said: "We will need international engagement."

"It is not possible to see a solution to this without some kind of international engagement that will protect the security of the Israeli people and will create the viability for open borders to be given to the Palestinian area in Gaza," he said.

Brown, who spoke shortly after an Israeli airstrike Tuesday on a UN-run school in Gaza, described the situation as a "humanitarian crisis."

"This is the darkest moment yet for the Middle East and it affects the whole of the world," he warned. (dpa)