GAZA CITY, Gaza Strip ? An Israeli helicopter fired a missile at Palestinian militants during a cross-border clash in northern Gaza early today, killing three and wounding four, Palestinian officials said.

The incident started with a gun battle across the border, and the helicopter responded by firing a missile, the officials said. Islamic Jihad said the militants involved were its members.

The Israeli military said soldiers spotted Palestinian militants about to launch rockets at Israel, so they opened fire and called in aircraft, sparking an hourlong battle.

In the West Bank early today, Palestinian security officials said two additional militants were killed in separate Israeli raids. An Al Aqsa Martyrs’ Brigades militant was killed in the Balata refugee camp next to Nablus, and an Islamic Jihad gunman died in a clash in the village of Qabatiyeh.

Tensions have been running high since Friday, when an Islamic Jihad commander was killed in an explosion in south Lebanon. The militant group blamed Israel and threatened revenge, though Israel denied involvement.

On Monday, Israel’s confrontation with Palestinian militants took a different turn. Israel’s interior minister informed four leading Hamas legislators from east Jerusalem that they must quit the Palestinian parliament if they want to continue living in the Israel-controlled city.

Interior Minister Ronnie Bar-On issued the ultimatum to Khaled Abu Arafa, the minister of Jerusalem affairs, and to Hamas lawmakers Mohammed Abu Teir, Ahmed Abu Atoun and Mahmoud Totach.

“You will either resign or you won’t be with us,” Bar-On said in a TV interview. “The letters were delivered to them today, and they have 30 days to decide.”

The four were summoned to accept the ultimatum notices at a Jerusalem police station. All refused to sign the letters and were released, police said.

Expelling Palestinians from Jerusalem for political reasons is unprecedented. It reflects the situation caused by the Hamas victory in January parliamentary elections and its formation of a government in March.