Israeli leaders on Wednesday authorized the army to send troops into residential areas of Gaza and gave the green light for the military to push ahead with a plan to create a buffer zone meant to prevent militants from firing rockets into Israel, officials said.

By late night Israeli tanks and armored personnel carriers advanced toward one of Israel's former settlements in northern Gaza, Palestinian officials and witnesses said.

It was unclear if the movement by Israeli forces toward the abandoned settlement of Nissanit — reported by Palestinian security officials and Palestinian witnesses — was part of that new offensive.

The Israeli military did not immediately confirm the movement

The Security Cabinet's decision, stepping up a ground offensive in Gaza, indicated Israel could be prepared to partially reoccupy Gaza less than a year after withdrawing all troops and settlements from the area.

Olmert convened an urgent meeting after Hamas militants fired rockets twice into the southern Israel. The first hit an orchard in the city of Ashkelon late Tuesday. A second rocket was fired at about the same time Wednesday, hitting the town of Zikim.

Although neither attack caused injuries, it was the first time a rocket has flown so far into Israel, signaling that militants have improved the range of the primitive weapons and escalating a crisis over a captured soldier.

Hamas' militant wing claimed responsibility for both attacks, which occurred at 9 p.m. local time.

Small towns and villages such as Zikim near the Israeli-Gaza border have often been hit by crude rockets fired by militants. But Ashkelon, a city of 110,000 people that is 8 miles from Gaza, had had been out of range until Tuesday, when it was hit by a rocket for the first time.

Olmert responded by saying it would have "far-reaching consequences," and on Wednesday his government authorized the Israeli army to enter populated areas in northern Gaza Strip.

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After the Security Cabinet meeting, Olmert and Defense Minister Amir Peretz met with top military officials to decide which parts of a broad invasion should be immediately implemented, including the possibility of the buffer zone.

Olmert's office denied the Cabinet had approved the formation of such a zone. But meeting participants said the ministers had all agreed that a standing plan by the army to create a buffer zone could be an effective way of preventing rocket fire.

It was not clear when or if the security zone would be established.

An official statement from Olmert's office gave no details about the military operation, but said the army would continue to go after Hamas militants and their infrastructure. It said the army has been ordered to "prepare for a phased and continuous" operation.

The operation's main goals remain to find the soldier kidnapped by Palestinian militants last week and to prevent rocket fire on Israeli towns and cities, the statement said. Israel refuses to negotiate with the militants holding Cpl. Gilad Shalit.

"There will be steps taken and they will be very serious," said Cabinet Minister Yitzhak Herzog, who refused to elaborate on the military's plans. "There is a very broad operation here. It will continue."

Countrywatch: Israel

Israel occupied a small strip of southern Lebanon for 18 years before withdrawing in 2000. A similar occupation in northern Gaza could be risky.

Israel could establish the security zone in its abandoned former settlements in northern Gaza, vacant lands that militants use to fire rockets and that Israel could seize with relatively little bloodshed.

If Israel wants a broader zone, however, it might have to enter the northern towns of Beit Lahiya and Beit Hanoun, which would likely lead to bloody street battles with militants.

Israel launched its offensive into Gaza last week after Palestinian militants kidnapped Shalit from a military post near the Gaza border. The army has been operating in Gaza, but has avoided sending troops into the strip's dense cities. The rocket attack on Ashkelon changed the equation.

Ahead of Wednesday's ministerial meeting, Israeli aircraft targeted the Palestinian Interior Ministry for the second time in a week, the Israeli military said. Witnesses said missiles hit the main structure and damaged a building next to the ministry. Rescue workers said five people were wounded.

The two top floors of the main building collapsed, and the second building, which provides housing for ministry employees, was set on fire, witnesses said.

In other attacks early Wednesday, Israeli aircraft fired missiles at a Hamas camp in southern Gaza and a Hamas-affiliated school in Gaza City, and shelled open areas in the north. A 13-year-old boy was seriously wounded in the head by shrapnel, Palestinian medical officials said.

The rocket fired by Gaza militants Tuesday flew 12 kilometers (7 miles) and exploded in the courtyard of a school in Ashkelon, a city of 110,000 on Israel's seacoast north of Gaza. School security cameras showed a large cloud of white dust rising from the point of impact. The school was empty at the time and no one was hurt.

Although militants have launched many of the small, homemade rockets toward Ashkelon, this was the first one to hit the center of the city. Militants have repeatedly claimed they were developing rockets with longer ranges.

In the hours before the rocket attack, Israeli forces were already operating in northern Gaza looking for tunnels, explosives, weapons warehouses and other facilities used by militants, according to the area army commander.

In a sign militant groups were stepping up their activity, soldiers on Wednesday caught a Palestinian militant in the West Bank with an explosives belt strapped to his waist and ready for use, the army said. The militant was caught in the West Bank settlement of Barkan before he had a chance to detonate his explosives, the army said.

Palestinian officials said the would-be bomber was a 17-year-old member of the Islamic Jihad militant group.

The Hamas-linked militants holding Shalit have demanded that Israel release hundreds of Palestinian prisoners in exchange for information about the captive soldier. On Tuesday, Olmert ignored a deadline to begin freeing the prisoner.

On Tuesday, Olmert ignored a deadline to free Palestinian prisoners set by the Gaza militants holding Shalit.

A spokesman for the Army of Islam, one of the three groups that abducted Shalit, said the militants would not release any information about the soldier until Israel complies with the demands. However, he said there were no plans to kill the soldier.

There has been a flurry of diplomatic activity throughout the region aimed at securing Shalit's release. The efforts have focused on Syria, where Hamas' top leadership lives.

A Palestinian official said Wednesday that Turkey had stepped up its efforts to secure a diplomatic resolution to the crisis.

On Monday, Ahmet Davudoglu, an adviser to Turkish Prime Minister Tayyip Erdogan went to Syria and met with Hamas leader Khaled Mashaal, who told him Hamas was prepared to be extremely flexible, but Israel had to be willing to negotiate as well, the official said.

The official spoke on condition of anonymity because he was not authorized to discuss the secret talks. Olmert has so far refused to negotiate with the militants.