Israel: ‘War to the bitter end’ against Hamas

Defence minister Ehud Barak said there would be no let-up until the Islamist group had been dealt a "severe blow".

As the Israeli navy joined in the pounding and tanks massed in a newly-declared buffer zone, he said the offensive, which has claimed 300 lives including at least 50 civilians, would be "widened and deepened" until it succeeded.

Today warplanes struck a house next to the Hamas prime minister's home and flattened a building at a university linked to the militants.

But the attempt to end the attacks on Israel from Gaza only goaded the Palestinians into a fightback: one Israeli civilian was killed and several were wounded as Hamas fired its rockets further into Israel than ever before.

Foreign Secretary David Miliband said killing civilians and children was unacceptable

"This is a very dangerous and very dark moment," he said.

Mr Miliband renewed calls for a ceasefire to end the bloodshed.

Faced with widespread criticism for the military action, Israeli foreign minister Tzipi Livni said her country was targeting militants but "unfortunately in a war ... sometimes also civilians pay the price".

Voicing "grave concern" at the situation, Mr Miliband said: "Any innocent loss of life is unacceptable.

"In this case there has been massive casualties, some of them civilians, some of them children and that's one of the reasons why we have called for a ceasefire.

"This is a very dangerous and very dark moment, partly because of the lives that have been lost and the humanitarian crisis that exists, partly because of the threat to the chance of a comprehensive peace that is so important for the Palestinians but also for Israel and thirdly for the fuel for radicalism."

Mr Miliband claimed a "terrible price" was now being paid for the "slow and faltering pace of negotiations" for a peace deal over decades.

He appeared to express solidarity with Palestinian president Mahmoud Abbas, whose Fatah party holds power in the West Bank but has lost control of Gaza to Hamas.

He said support should be given to leaders who are committed to peaceful negotiations.

But the exiled leader of Hamas, Khaled Meshaal, called for a new intifada, or uprising, against Israel, while its leader in Gaza, Ismail Haniya, condemned the Israeli attacks as an "ugly massacre".

Gordon Brown has spoken to Israel's prime minister Ehud Olmert as the international community urges both sides in the Middle East clashes to show restraint.

The UN Security Council has called for a halt to the violence, but US President George Bush's administration, in its final weeks in office, has put the onus on Hamas to renew the truce.