Twenty-four Palestinians, including at least 9 civilians, were killed late Friday and early Saturday in escalating Israeli-Palestinian fighting that renewed threats of an Israeli invasion of Gaza and clouded peace efforts. A baby and two teenagers were among the dead, and dozens of people were wounded.

In all, 57 people have died since clashes between Israel and extremists affiliated with Gaza's ruling Hamas movement spiked Wednesday. At least 24 were civilians, the youngest a 6-month-old boy. An Israeli man was also killed by Palestinian rocket fire that grew more ominous earlier this week when it struck closer to Israel's heartland.

Hamas said the baby, Malak Karfaneh, died just before midnight Friday in an Israeli strike on Beit Hanoun, a northern town where Palestinian militants often launch rockets at nearby Israel. But local residents said one of those rockets fell short and landed in the area of the baby's house.

The Israeli military, which sent troops, tanks and aircraft after Gaza rocket squads, said it only attacks rocket-launching operations, but noted that militants sometimes operate within civilian areas. On Saturday, it said troops identified 15 hits in its operations against rocket squads and militants laying explosive devices against Israeli targets.

Fierce fighting Saturday erupted near the northern town of Jebaliya, pitting Israeli troops backed by tanks and attack aircraft against Palestinian militants launching crude rockets and mortars.

Among those killed were at least nine militants, but also at least eight civilians -- including a 17-year-old girl and her 16-year-old brother, a 45-year-old man and his 20-year-old son, and two sisters thought to be in their early 20s.

The sisters and another civilian were killed by tank shells that struck two houses in separate attacks, Palestinian officials said. Rescue teams evacuated a 7-month-old boy from one of the houses, unharmed.

The Israeli military said it would look into reports of tank shells hitting houses.

Tareq Dardouna, a resident of the Jebaliya area, told The Associated Press that a relative was killed outside his home in the crossfire that began raging at 3 a.m.

"His body is still on the ground," Dardouna said in a telephone interview from his home, where he was tending to four wounded people. "Ambulances tried to come, but they came under fire. ... We are in a real war."

The Israeli military said five soldiers were wounded in the clashes. Nearly two dozen rockets landed Saturday in southern Israel, including three that struck in and around the city of Ashkelon, 17 kilometers (11 miles) north of Gaza, the military said. Two children and a woman were slightly wounded in the Ashkelon attacks, the military said.

Hamas fighters were unbowed by the spiraling violence.

"The Zionist forces failed in Gaza before," said Abu Obeida, a spokesman for Hamas' military wing. "We will respond to any aggression...with every available means."

Israel evacuated its troops and settlers from Gaza in late 2005, but militants proceeded to fire rockets from the abandoned territory. On Thursday, militants raised the stakes significantly by firing Iranian-made rockets into Ashkelon, a coastal city of 120,000 people.

While Ashkelon had been targeted sporadically before, it never suffered direct hits. The assault increased the pressure on Israeli Prime Minister Ehud Olmert to protect a widening circle of people at risk.

Next week, U.S. Secretary of State Condoleezza Rice plans to visit the region to try to prod Israel and moderate Palestinians forward in their bid to reach a peace accord by the end of the year. The two sides declared that goal at a U.S.-sponsored conference in November.

Senior European diplomat Javier Solana will also visit the region beginning Sunday, to encourage Israeli and Palestinian leadres to keep the peace process on track, his office said in a statement.

But Palestinian President Mahmoud Abbas' efforts are compromised by the fact that he only rules the West Bank, while Gaza is controlled by the violently anti-Israel Hamas. And Israel's fragile governing coalition would be hard pressed to make concessions to the Palestinians while Gaza militants pummel southern Israel with rockets.

Palestinian rockets with increasing range have put tens of thousands of Israelis in jeopardy, and on Friday, Israeli leaders warned of an impending invasion because of the growing menace.

Israeli Deputy Defense Minister Matan Vilnai said Friday that Israel had "no other choice." And Defense Minister Ehud Barak said the assaults on Ashkelon "demand an Israeli retaliation."

Barak, who has warned repeatedly of a large-scale military operation in Gaza, blamed Hamas for the rise in violence and said the militant movement would "suffer the consequences."

On Friday, Abbas called on Israel to stop all attacks in Gaza and urged Palestinian militants to halt the rocket fire. "It is in the interest of the Palestinian people not to give Israel any pretext to continue its aggressions," a statement from his office said.

U.S. State Department spokesman Tom Casey denounced Hamas' rocket attacks as "completely unacceptable" and demanded they stop. He also said the U.S. regularly urges Israel to consider the consequences of its actions and to pay careful attention to the humanitarian needs of the Palestinian people.