Israel shifted the focus of the fight to free a kidnapped soldier in Gaza today, saying that Hamas was now "front and centre" in its confrontation with Palestinian militants.

An urgent Security Cabinet meeting this morning approved a series of measures, including more airstrikes against Hamas leaders and buildings, to step up the military campaign to secure the release of Corporal Gilad Shalit, who was taken hostage by Palestinian gunmen on June 25.

"There will be steps taken and they will be very serious," said Yitzhak Herzog, the Israeli Tourism Minister, after the meeting. "There is a very broad operation here. It will continue."

An Israeli Foreign Ministry spokesman told The Times that a rocket attack last night on the Israeli town of Ashkelon, claimed by Hamas, had shown the "nature of the organisation" and justified retaliation against the Palestinian ruling party, which took power in January.

"From the Israeli point of view, the shooting of the Qassam [a rocket favoured by Palestinian militants] into a school in Ashkelon is a dangerous escalation in Hamas's war against the Israeli civilian population and we will have to take appropriate counter-measures to deal with the threat," said Mark Regev.

Mr Regev declined to comment on Israeli press reports that Ehud Olmert, the Prime Minister, had also approved an extension of the so-called "security zone" in the northern Gaza Strip, where Israeli soldiers go from house to house, looking for militants planning attacks.

The ramping up of the Israeli military campaign to free Corporal Shalit, dubbed "Operation Summer Rain", comes after a deadline set by his Palestinian kidnappers passed yesterday without the death of the soldier.

The armed wing of Hamas is believed to be one of three groups holding the 19-year-old corporal. At a Palestinian Cabinet meeting depleted by the arrest of eight ministers by Israel, Ismail Haniya, the Palestinian Prime Minister, urged the captors not to harm him.

Last night's rocket attack, which hit an empty school far beyond the usual range of Palestinian missiles raised fears that Hamas had upgraded its weaponry and prompted Mr Olmert to threaten a serious response. Hours later, the Palestinian Interior Ministry was bombed by Israeli aircraft for the second time in a week.

The ongoing crisis, and the massed presence of Israeli troops and tanks on the edge of the Gaza Strip has raised the question of whether Israel intends to move troops back into territory that has evacuated last summer for the first time in 38 years.

Pressure is also mounting on Mr Olmert, who is keen to reinforce his security credentials. A columnist in Yediot Aharanot, Israel's best selling newspaper, today urged Mr Olmert to "take the gloves off".

"Mr Olmert is caught on the horns on this one," said Stephen Farrell, The Times Middle East correspondent. "He is under a lot of pressure to control the area. On the other hand, Israeli soldiers were in Gaza for 38 years and they didn't stop the rockets then."

"Also Mr Olmert has defined the purpose of his first term as the withdrawal from parts of the West Bank and the fixing of Israel's borders. That's going to be much harder to sell if he sends soldiers back into the Gaza Strip."

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