GAZA CITY, Gaza Strip - Israel pummeled Gaza with air and ground fire while rockets fired by Palestinians slammed into southern Israel yesterday.

The violence threatened to derail recently resumed peace talks.

The Israeli attacks killed an extremist leader and one of his female relatives along with five others in Gaza.

Prime Minister Ehud Olmert vowed to strike Palestinian attackers "without compromise, without concessions and without mercy." But he gave no hint a large-scale offensive was near.

The widening violence has clouded Israeli-Palestinian peace talks, resumed after a Mideast conference in November sponsored by President Bush.

Yesterday, a spokesman for Palestinian Authority President Mahmoud Abbas told the Associated Press the violence was calling into question further talks. "No one can proceed with negotiations when the situation is like this," Nabil Abu Rdeineh said.

Gaza attackers, led by Hamas, fired dozens of rockets and mortars at Israeli towns. The rockets caused no serious injuries but further traumatized residents who have been putting up with daily barrages for months.

Israel struck back at northern Gaza, targeting rocket squads and areas that attackers frequently use.

A leader of the small Hamas-allied Popular Resistance Committees, Raad Abu al-Ful, and a female relative were killed when a missile hit their vehicle, the faction said. Earlier, Palestinian officials said the relative was Ful's wife.

The Popular Resistance Committees pledged retaliation.

After nightfall, Israeli aircraft targeted a car in northern Gaza, but, according to Palestinian hospital officials, killed a woman and her son on a donkey cart next to the vehicle and an unidentified man.

Israeli aircraft later fired missiles at a car south of Gaza City, killing two Hamas fighters and wounding three others, Hamas officials said.

Direct Hamas involvement in the rocket attacks is a new development this week.

Since June, when the Islamic extremists overran Gaza, ending Abbas' writ there, they had allowed other groups to freely fire rockets at Israel. That changed Tuesday, when Israel sent special forces into Gaza, setting off a daylong battle that was the biggest in months.

Thirty Palestinians, including a son of Gaza's Hamas strongman, Mahmoud Zahar, have been killed since the violence escalated Tuesday. Most were extremists.

Hamas and other groups have fired more than 150 rockets and mortars since Tuesday, according to the Israeli military.

Yesterday, Olmert acknowledged there was "no magic formula" to stop the salvos, but he warned at a business conference in Tel Aviv that Israel would not stand for the relentless rocket fire.

Israeli Defense Minister Ehud Barak also talked tough, pledging to "continue until the rocket fire stops, and if necessary, we will intensify operations."

Barak was speaking after conferring with his commanders in the Gaza region. Earlier he met with senior brass in Tel Aviv and ruled out a large-scale ground operation in Gaza, at least for now, according to defense officials who spoke on condition of anonymity because the consultations were in private.

Israel's vaunted military has been baffled by the low-tech, homemade rockets with a range of only a few miles that have been plaguing Israel's south for years.

Air strikes and pinpoint ground operations have killed hundreds of Gaza extremists, and invasions have caused widespread casualties and damage - but none of the measures has stopped the rocket fire for long.

Father-to-Father Condolences

The father of an Israeli

soldier held captive in the Gaza Strip said yesterday that he sent a letter of condolence to Hamas strongman Mahmoud Zahar, whose son was killed Tuesday in an Israeli raid.

Zahar confirmed

to Israel's Yedioth Ahronoth newspaper that he had received Noam Schalit's letter. Gunmen affiliated with Hamas captured Cpl. Gilad Schalit in June 2006 in a cross-border raid.

"It was a personal

letter of condolences," Schalit said. He said he did

not appeal to Zahar

to help free Gilad, 21, but declined to disclose the text of the letter.

Zahar's son

Hussam, 24, a Hamas member, was one of 19 Palestinians killed in an Israeli operation. Scenes of Zahar weeping as he kissed his dead son's forehead were shown on Israeli TV on Tuesday.

- Associated Press