Gaza ceasefire strained as Mitchell flies in

Washington's newly appointed special envoy to the Middle East arrived in the region yesterday as the nine-day-old Gaza ceasefire came under its most serious strain yet after an Israeli soldier and a Palestinian died in border clashes.

The former senator George Mitchell will hold talks with Egypt's President Hosni Mubarak today in the wake of a bullish declaration by Barack Obama that the "moment is ripe" for peace talks, despite splits between Palestinians and an Israeli election tipped to put the right-wing Likud party in power.

The Israeli soldier was killed and three others injured when militants detonated a bomb close to the Kissufim border crossing. Medics said the Palestinian killed shortly after the attack on the Israelis was a 27-year-old farmer. Hours later a militant in the small Palestinian Resistance Committees was wounded, along with a bystander, as he rode on a motorcycle in southern Gaza.

Residents in the central Gaza town of Deir el Balah said tanks and armoured bulldozers were on the move, apparently preparing to retaliate.

Israeli politicians were quick to denounce the border bombing. The Defence Minister and Labour Party leader Ehud Barak said the country "cannot accept" the attack. "Any group that harms us will be dealt a heavy blow," he warned. "We will respond, but there is no point elaborating." The Foreign Minister Tzipi Livni said she did not care whether Hamas or another faction had been responsible for the attack. "Hamas controls Gaza and is responsible for everything that happens," she said. "Whenever they fire at me from Gaza, set off a bomb or launch a missile or smuggle (weapons), Israel will respond." Ms Livni, who is the leader of the governing Kadima party, is the main obstacle to Benjamin Netanyahu's Likud winning power in the elections next month.

The ministers' stance won backing from Hillary Clinton, President Obama's Secretary of State, who said: "We support Israel's right to self-defence. The (Palestinian) rocket barrages which are getting closer and closer to populated areas cannot go unanswered." While no armed Palestinian faction had claimed responsibility by mid-evening, the Hamas spokesman Sami Abu Zuhri said the bomb attack on the troops had been, "a natural response to the crimes of the occupier".

Israel closed crossings into Gaza last night in response to the killing of the soldier, temporarily halting the flow of humanitarian aid and other supplies which aid agencies had been pressing Israel to expand. They are trying to get supplies to civilians displaced by the destruction of up to 20,000 homes during the 22-day Israeli offensive.

Peter Lerner, spokesman for the Israeli military's co-ordination office for the Gaza borders, said: "This is another example of terrorist activities against the crossings, the same crossings that serve the Palestinian people for... aid."

Egyptian mediators are seeking to broker a longer term truce – of up to18 months – between Hamas and Israel. Mr Mitchell will go on from Cairo to Jerusalem today for talks with Israeli and moderate Palestinian leaders.

On the eve of his envoy's tour of the Middle East, President Obama told the Dubai-based Al-Arabiya TV news channel: "The moment is ripe for both sides to realise that the path that they are on is one that is not going to result in prosperity and security for their people. And that instead, it's time to return to the negotiating table."