By Nidal al-Mughrabi
GAZA (Reuters) - Israeli troops battled Palestinian militants on the outskirts of Gaza City on Sunday after tanks thrust deep into the coastal strip in an invasion that marked the worst fighting in the conflict in decades.
The Islamist group Hamas said it had captured two Israeli soldiers, an event which would highlight the political risk domestically for Israel of sending in its troops. The Israeli army could not confirm the report.
The long-predicted ground action followed a week of Israeli bombardments from land, sea and air which failed to halt Hamas rocket attacks on southern Israel but killed more than 450 Palestinians in the crammed, Hamas-ruled Gaza Strip.
Israeli tanks and troops virtually cut the territory in half in a night-time advance and by Sunday morning were ringing Gaza City itself, Palestinian witnesses said.
Soldiers and Hamas fighters were locked in gunbattles east of the Hamas stronghold of Zeitoun.
"They have come to where we wanted and they will soon receive our gifts," a Hamas officer near the frontline said.
In initial clashes, Israeli ground forces killed eight Gazans, five of them fighters. Four Palestinians were killed when a house was struck by an Israeli missile in Rafah, medics and residents said.
Israel said 30 of its soldiers were wounded, two seriously, since the start of the ground assault. Israeli aircraft struck more than 45 targets, including arms smuggling tunnels, weapons depots and mortar squads.
"During exchanges of fire overnight, dozens of armed Hamas operatives were hit," an Israeli military communique said.
At the United Nations, the United States thwarted an effort by Libya to persuade the Security Council to call for an immediate cease-fire, diplomats said.
Israel said it called up tens of thousands of reservists and the military's chief spokesman estimated the operation could take "many long days."
Heavy casualties are likely to increase international pressure on Israel to halt its biggest operation in the Gaza Strip in four decades, fighting that holds significant political risks for Israeli leaders ahead of a February 10 national election.
The plight of the 1.5 million Palestinians crammed into the Gaza Strip was growing more desperate. People have taken shelter in their homes for days and humanitarian agencies warned that water, food and medical supplies were running short.
IT WON'T BE SHORT
Israeli Defence Minister Ehud Barak said the aim of the ground push was to protect southern Israel from Hamas rocket attacks. He refrained in a televised address from making any threat to try to topple Gaza's Hamas government.
"It won't be easy. It won't be short," said Barak, leader of the centre-left Labour party and a candidate for prime minister in the election.
A spokesman for Hamas's armed wing, the Izz el-Deen al-Qassam Brigades, said Israeli troops faced certain death or capture. "The Zionist enemy must know his battle in Gaza is a losing one," spokesman Abu Ubaida said.
At least a quarter of the 453 Palestinians killed in the current conflict have been civilians, a U.N. agency said. Another 2,050 Palestinians have been wounded.
Four Israelis have been killed by rockets in southern Israel.
The United States, Israel's main backer, said a cease-fire should take place as soon as possible but should guarantee an end to Hamas rocket attacks.
A spokesman for Palestinian President Mahmoud Abbas condemned the Israeli attack as "a vicious aggression."
(Writing by Angus MacSwan; Editing by Janet Lawrence)