Violent protests against the Israeli withdrawal from Gaza spread to the centre of Jerusalem on Wednesday. Angry settlers blocked the main road to the city and police used water cannon to scatter the protesters, many of them children.

Earlier, Israeli soldiers fired their weapons into the air to disperse stone-throwing settlers attacking Palestinians at the Gush Katif settlement in Gaza, which is to be abandoned in August as part of Prime Minister Ariel Sharon's withdrawal plan.

In recent days, Gush Katif's 8,500 residents have been joined by ultra-nationalist settlers from the West Bank determined to block the retreat.

An opponent of Israel's planned pullout from the Gaza Strip and part of the West Bank is detained by police. (AP photo)

Organizers bused an estimated 3,000 right-wing extremists into the settlement to protest Israel's planned withdrawal. They took over a house in the Palestinian village of Amawassi, raised Israeli flags and scrawled slogans, including "Death to Sharon" and "Muhammad was a pig."

It's not clear which side threw the first stone, but a brawl was soon underway. A Palestinian youth was badly injured by Israeli protesters. When an Israeli soldier dragged the injured youth to a corner, cameras captured the protesters throwing stones at him as he lay on the ground.

"Let him die," they shouted to the Israeli soldier protecting him.

An arrested and handcuffed demonstrator makes a victory sign from inside an Israeli police bus. (AP photo)

Long-time Jewish residents of Gush Katif were appalled and the government says that while the settlers have the right to protest peacefully, it will not tolerate breaking the law.

"I think there is a very clear red line where you cross this legal threshold and you fight your own institutions ... This is totally unaccepted and we won't let it go," said Eiyal Giladie, an Israeli official co-ordinating the withdrawal.

In the evening, Israeli troops went in a second time and forcibly cleared the protesters out of the building and put them under arrest.

Most of the protesters are staying at a hotel in the settlement that they say they plan to turn into a fortress. But the Israeli military has other plans for the hotel, declaring it a closed military zone, meaning no one can go in or out. It also suggests the army plans to clear it out, by force if necessary.

The protests also reached beyond Gaza.

About 6,000 police failed to stop demonstrators from blocking highways. On one section protesters poured oil and nails on the road.

Israel's actual withdrawal from Gaza and a few settlements in the West Bank is still 47 days away and many here fear the protests will grow. For his part, Sharon is promising to put an end to what he called the wild behaviour of a "fellowship of thugs."