Israeli helicopters carried out air raids against four targets in Gaza (search) early Friday, retaliating for a Palestinian rocket attack that killed a young Israeli woman. The surge in violence shook a five-month truce already threatened this week by a suicide bombing.

Palestinian leader Mahmoud Abbas (search) declared a state of emergency in Gaza in light of the deteriorating situation there, Israeli media reported Friday.

Two rockets exploded Thursday afternoon in the village of Nativ Haasara (search), one of them hitting a house and killing a woman in her 20s, the military said. The second destroyed a parked car.

Rockets also hit an army base and a Gaza settlement, slightly wounding several Israelis, according to the military and media reports.

A Palestinian militant group, the Al Aqsa Martyrs' Brigades (search), said the attacks were its response to the Israeli killing of a militant earlier in the day. The Islamic Hamas also claimed responsibility, according to media reports.

The army said the man killed in Nablus was a local militant leader and was planning attacks against Israel.

Israel responded to the woman's death with helicopter attacks against the four sites in Gaza, witnesses said.

Three missiles struck a building used by Hamas as a cultural center in northern Gaza, residents said. In the south, witnesses said the choppers fired on two sites used by Palestinians to launch rockets against settlements. Then helicopters fired missiles at a metal workshop in central Gaza.

The Israeli military said the targets in the two southern Gaza raids were also used by militants to store weapons, and the metal workshop was used for making weapons. The military had no comment about the northern Gaza raid.

Earlier, the Israeli military posted roadblocks on main Gaza roads, cutting the narrow seaside strip into three parts.

David Baker, an official in Prime Minister Ariel Sharon's office, charged that the Palestinian Authority was responsible because of its "refusal to fight terror." He added, "We will not allow our citizens to be murdered, and if the Palestinian Authority doesn't take necessary steps to prevent terror, we will."

Palestinian Interior Minister Nasser Yousef (search) ordered his police to stop the rocket fire. Both the Israelis and the Palestinians have an interest in maintaining the calm at least until Israel completes its pullout from Gaza and part of the West Bank in the summer.

In a confrontation at nightfall, Palestinian police shot and wounded five Hamas gunmen who refused to stop at a northern Gaza roadblock, security officials said. Gunmen then attacked police stations with gunfire and grenades. No injuries were reported.

Abbas, who harshly condemned the suicide bombing on Tuesday that killed five people, also criticized the Israeli raid into Nablus and called on all sides to show restraint.

"That is what we call a cycle of dirty violence," he said. "We believe that this will lead only to the destruction of the peace process."

Islamic Jihad has attacked several Israeli targets in recent months, including the suicide bombing outside a shopping mall in the Israeli seaside city of Netanya on Tuesday evening. The fifth victim, a soldier, died Thursday.

After the bombing, Sharon ordered his security forces to target Islamic Jihad leaders.

U.S. Secretary of State Condoleezza Rice has told Abbas he must take immediate action to find and prosecute those responsible for the suicide bombing.

"While we welcome President Abbas' condemnation of this heinous attack, we now are looking to the Palestinian Authority to take some concrete steps to bring those who planned and support this attack to justice," State Department (search) spokesman Tom Casey said Thursday.

Soldiers surrounded the Nablus house where Alassi was staying Thursday and demanded he surrender, said Maj. Sharon Asman. Alassi and another militant fled, and the soldiers ordered them to stop. One man returned to the house and was arrested, but Alassi continued running and was shot and killed, he said.

The raid took place at the home of Hannah Alassi, 67, a British citizen who moved to Nablus in 2002 and was not related to the fugitive.

The army said Hannah Alassi was an activist who gave refuge to militants. Hannah Alassi said she was a journalist who made television documentaries and filed stories to radio stations and magazines on the Middle East conflict.

Visiting German Foreign Minister Joschka Fischer scolded the Palestinians for failing to stop militants and warned "there will be no chance to establish an independent Palestinian state as long as violence and terrorism continue."

The upsurge in violence comes a month before Israel's pullout from the Gaza Strip and part of the West Bank.