JERUSALEM (Reuters) - A Palestinian man threw a chemical substance believed to be acid at an Israeli family in the occupied West Bank on Friday, injuring a man and four children, Israeli police and the military said.

The assailant was shot and wounded immediately after the attack, which took place at a checkpoint south of Jerusalem.

Police spokeswoman Luba Samri said the attacker had "poured an unknown substance suspected to be acid on a Jewish family." She said a civilian at the scene shot and wounded the assailant.

The Israeli military said the Israeli man had stopped to pick up the Palestinian as a hitchhiker and then the attack occurred.

The incident comes at a time of heightened tension between Palestinians and Israelis, particularly in the West Bank and East Jerusalem, territories Israel seized in a 1967 war and Palestinians want for an independent state, together with Gaza.

There was no immediate claim of responsibility for the attack.

Over the past four months, 10 Israelis and a foreign visitor have been killed by Palestinians in knife or car-based attacks, while at least a dozen Palestinians have also been killed, including most of those who carried out the killings.

On Wednesday, a Palestinian minister died shortly after a confrontation with an Israeli border policeman in the West Bank. The policeman grabbed the minister by the neck during a scuffle and minutes he collapsed with breathing problems.

An Israel official who attended the autopsy said the minister had died of a heart attack possibly brought on by stress, while the Palestinian pathologist concluded that the grab to the neck more directly lead to heart failure.

In the Gaza Strip, tens of thousands marched in celebration of the 27th anniversary of the founding of the Islamist Hamas group, in the largest show of support for the organization there since a five-week war with Israel that ended in August.

In the hostilities, more than 2,100 Palestinians were killed, most of them civilians, Palestinian officials said. More than 70 Israelis were also killed, most of them soldiers.

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Fathy Hammad, a former cabinet minister, saw the large turnout as showing Hamas remained popular despite the war's devastation and the hardships of an Egyptian and Israeli blockade of the coastal territory.

"Once one road is blocked, another one opens," Hammad said.

But he cautioned against Palestinian frustration with what they see as a slow pace of efforts to rebuild homes and other property, warning this could bring about further confrontation.

"We will extract reconstruction by our rifles, if there will be no rebuilding, there will be another explosion," Hammad told those gathered at a rally in Gaza's Jebalya refugee camp.

(Additional reporting by Nidal al-Mughrabi in Gaza; Writing by Allyn Fisher-Ilan, editing by Luke Baker)