AT LEAST 20 Palestinians and 1 Israeli soldier were killed yesterday in the worst clashes since Israeli troops moved back into the Gaza Strip last week.

The Israeli army said that its forces came under “continuous” fire from anti-tank missiles and rocket-propelled grenades as its tanks reoccupied three Jewish settlements abandoned last year. An Arabic television channel said that the soldier was killed by sniper fire.

The advance was met by heavy resistance from Hamas and other militant groups. At night the streets of Gaza’s northernmost towns, Beit Hanoun and Beit Lahiya, are deserted except for bands of gunmen armed with missiles and heavy machineguns.

Red tracer fire illuminates the skyline but gunmen are often unable to identify friend from foe. Two al-Jazeera journalists were shot and injured on Wednesday by militants who mistook them for Israeli undercover soldiers.

After the highest Palestinian death toll for two years, women and children began evacuating buildings closest to the settlements, which at night become fortresses of militants, who can be seen carrying bombs with protruding electrical cables, to bury them in alleys and near roads.

Palestinians claimed that the deadliest attack, an Israeli air strike near Beit Lahiya, killed six Palestinian civilians. Israel’s army said that it carried out two air strikes against armed militants, killing four gunmen. Apache helicopter gunships joined in the attacks.

Visiting the wounded at Gaza’s main hospital, Ismail Haniya, the Palestinian Prime Minister, last night called for international intervention to stop the offensive.

Israel says that its Operation Summer Rains is intended to secure the release of the captive Corporal Gilad Shalit, and to stop Palestinian militants firing Qassam rockets into Israel.

Ehud Olmert, Israel’s Prime Minister, has refused to negotiate, but the missing soldier’s father, Noam Shalit, last night said that he did not expect the Palestinians to give up his son for nothing. “Everything has a price. I don’t think there will be any sort of move to free Gilad without a price,” he told Army Radio. “That’s not the way it works in the Middle East.”

The clashes have intensified after a new generation of Hamas’s home-made rockets began landing in the town of Ashkelon in the past two days.

Israel has in return fired thousands of rounds of 155mm heavy artillery into Gaza, pausing briefly last month after eight Palestinians were killed at a beach picnic while Israel was shelling the coast.

Israel’s military exonerated itself after an internal investigation, and the land-based shelling and coastal firing resumed after the seizure of Corporal Shalit, 19, in a cross-border tunnel raid by militants.

As she walked out of the area with three of her nine children, Hanad Tayyah, a widow, said that she was certain the fighting would escalate. “We are going because the Israeli tanks have fired many shells in front of our buildings,” she said.

The clashes, she added, were the worst she had seen during seven years living in northern Gaza, although she had been forced to leave “many times” before, and sighed with frustration over the issue of continued firing of rockets by Palestinian militants.

“I don’t know. Sometimes I say they [militants] have the right to do that. Sometimes I change my mind. The rockets have no benefit and the Israeli reaction is much bigger than our own,” she told The Times.

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