JENIN, West Bank (Reuters) - The Israeli army killed four Palestinians, at least three of them gunmen, Tuesday as it blockaded Palestinian inhabitants in the West Bank and Gaza Strip during Israel's election day.

Three Palestinians were killed when an explosion levelled a house owned by an Islamic militant in Gaza. Palestinians said the house was hit by an Israeli helicopter missile. The Israeli army said the three were killed while making bombs.

Palestinian medics said three Palestinian gunmen were shot dead in the northern West Bank city of Jenin during an exchange of fire with Israeli troops and that a 17-year-old was killed while running to the aid of one of the gunmen.

The army said the teen-ager was also armed and took part in the firefight with troops during an operation to seize militants involved in a 28-month-old uprising for a Palestinian state.

A Palestinian photographer working for Agence France Presse was shot in the leg during the incident, the medics said.

Captain Sharon Feingold, an army spokeswoman, said the photographer may have been hit by shrapnel from the gunfight. "He was not targeted. We do not target journalists," she said.

As Israelis began voting in their general election, 3.6 million Palestinians living in the West Bank and Gaza Strip were barred by Israel's military from traveling between Palestinian towns and villages and entering Israel.

Israeli security officials said the ban was issued due to intelligence information that Palestinian militants were planning attacks to disrupt the election. Palestinians condemned the measure as collective punishment.

Palestinian residents of the West Bank cities of Tulkarm, Qalqilya, Nablus, Bethlehem, the Israeli-ruled parts of Hebron as well as Jenin were also under strict military curfew.

MILITARY CLAMPDOWN

Israel's military reoccupied six Palestinian-administered West Bank cities last year after a spate of suicide bombings and has frequently imposed curfews.

Palestinians identified the three dead in Gaza City as two children of Hamas militant Mohammed Salameh, including a 15-year-old girl, and a bodyguard of a senior Hamas leader, and said they were killed in a helicopter missile strike.

Israel said they were killed when bombs being made by two of them, whom it called Hamas militants, detonated prematurely.

The large house was devastated by the explosion.

Mourners, many of them masked Islamic militants, carried the bodies of the three dead wrapped in green Hamas flags through the streets of Gaza City amidst cries of revenge.

"Sharon, prepare the coffins!" they shouted, in reference to Israel's right-wing Prime Minister Ariel Sharon who, much to Palestinian dismay, is expected to win Tuesday's election.

Sharon has taken tough military action against Palestinian violence and said peace talks envisaging a Palestinian state in the West Bank and Gaza, which deadlocked shortly before the revolt began, will resume only once militant attacks cease.

Talks between Palestinian factions on a possible cease-fire broke up on in Cairo Monday night without result.

Violence escalated in the days before the election. After a southern Israeli town came under rocket attack, the Israeli army launched its deepest raid into Gaza City since the Palestinian revolt began in September 2000. Twelve Palestinians, at least seven of them gunmen, were killed.