Tel Aviv/Gaza  - Israeli troops pushed further into the Gaza Strip Sunday morning, battling Palestinian militants in the north of the salient as they advanced on Beit Lahia and Beit Hanoun, supported by air attacks.

An Israeli military spokesman said 30 soldiers were wounded in overnight fighting, including two seriously.

Palestinian medical officials spoke of 17 killed, and 130 wounded, since the Israeli ground operation began. At least four of the dead were civilians who were killed by an Israeli tank shell.

The Israeli military spokesman dismissed as a "complete lie" militants' claims that they killed nine Israeli soldiers and a senior Israeli military official said reports that an Israeli soldier had been captured by the militants was "untrue."

The official, speaking on condition of anonymity, said that most of the resistance the Israelis have encountered so far has come from mortars and there has been relatively little close-quarters combat.

"We are operating in a very challenging area that has been well-prepared by Hamas in order to repel attacks," he said.

According to the Israeli media, Hamas can call on 16,000 armed fighters, and the organization's arsenal includes 4,000 rocket- propelled grenade launchers, 120 tonnes of explosives, and dozens of 120mm mortars.

The Israeli official said that although the Israeli ground incursion was proceeding as planned, it would not be a rapid operation which would end in days.

Israeli Prime Minister Ehud Olemrt told ministers at the start of Sunday's cabinet meeting, held in Tel Aviv, that the Israeli assault was "unavoidable" and was part of the overall Israeli operation, designed to "create a new security reality" for residents of southern Israel.

Media reports, which could not be confirmed, said the Israeli troops have managed to divide the Strip into three separate areas.

Concurrent with the ground fighting, the Israel Air Force attacked over 45 targets in the Strip overnight, including tunnels, weapons storage facilities, mortar shell launching squads, and a number of mortar shell launching areas, a statement by the Israeli military said.

The Israel Navy also attacked several targets including the Hamas intelligence headquarters in Gaza City, rocket launching areas, and Hamas marine forces outposts the statement added.

The Israeli ground operation got underway Saturday evening as infantry and armour, backed by combat engineers and with air support overhead, crossed into the salient after an artillery barrage lasting hours.

Palestinian militants immediately confronted the Israelis, sparking what the Islamic Hamas movement, which controls Gaza, said in a statement were "heavy and tough exchanges of fire and armed clashes."

Reports from inside the strip described explosions, heavy machine- gun fire and shelling by Israeli tanks. The bombing campaign continued overnight, and television footage from Gaza showed fires and billowing smoke.

The Israeli military said the ground operation was the second stage of the Israeli offensive, which began December 27, and was intended to destroy Hamas installations in the area of operations and to impede militants' firing of rockets at Israel.

Israeli Defence Minister Ehud Barak warned in a televised statement Saturday night that the ground campaign would be neither easy nor short.

The entry of ground troops into Gaza had been expected for days, after Israel called up and deployed thousands of reservists along the border, while the air offensive continued unabated.

Israel launched its "Operation Cast Lead" in response to a week of heavy rocket barrages on the Jewish state out of the Gaza Strip, following the end of a shaky six-month truce between Israel and Hamas leaders in the territory.

At least 461 Palestinians were killed in the hundreds of Israeli strikes and around 2,300 wounded in the air strikes.

The approximately 450 Palestinian rockets and mortars launched since the start of the operation have left four Israelis killed, three of them civilians, and dozens more wounded.

The United Nations Relief and Works Agency (UNRWA) has said that at least a quarter of the Palestinian casualties are civilian.

In New York, the United Nations held an emergency meeting after the start of the Israeli invasion but was unable to reach agreement on a resolution. dpa