GAZA CITY -- Gunfire and explosions raged across Gaza City yesterday, killing at least 21 people in the most widespread fighting in nearly a year of clashes between the rival Fatah and Hamas movements.
The infighting threatened to destroy a fragile unity government established in March and pushed Palestinians ever closer to all-out civil war.
Street battles turned the densely populated seaside city into a war zone, putting terrified civilians increasingly at risk.
Stray bullets damaged apartment buildings, gunmen fired at a group of protesters, and Hamas militants beat a female Fatah lawmaker and her two children before setting fire to her apartment.
Hamas also targeted Israel, firing barrages of homemade rockets for a second day, seriously wounding one person and knocking out power in the southern Israeli town of Sderot, officials said. Israel staged two airstrikes on Hamas targets, reportedly killing five people.
Hamas fighters appeared to be trying to draw Israel into the conflict in hopes of uniting Palestinians against a common foe. Israeli Prime Minister Ehud Olmert's Security Cabinet decided against large-scale reprisal, however, although it authorized the army to step up attacks on Hamas rocket squads.
"Israel cannot continue to restrain itself when its citizens are being hit and therefore decided on a severe and serious response," Olmert's office said.
A main goal of the March Hamas-Fatah alliance was to halt months of factional violence, but the unity deal never addressed a key area of dispute -- control over Palestinian security forces.
The latest round of violence erupted this week after President Mahmoud Abbas of Fatah deployed thousands of police officers to halt a crime wave in Gaza without first consulting with Hamas. Forty-five people have died, most of them Fatah men, and dozens have been wounded.
During the week, the attacks have grown increasingly brazen. Hamas gunmen fatally shot six bodyguards early yesterday during an assassination attempt on a top Fatah security official.
The commander, Rashid Abu Shbak, wasn't home during the assault and his family escaped harm.
Hamas militiamen also set fire to an 11-story apartment building inhabited by several Fatah officials. Fatah lawmaker Nema Sheik Ali, the wife of a top security commander, said the gunmen broke into her fifth-floor flat, beat her and two of her children with their weapons, and then set the home ablaze.
"They came, they broke the door," she said. "They assaulted my children and they pushed me aside, then they torched the apartment."
Ali's family managed to flee the building. But many residents were trapped inside, screaming out their windows for help.
Shadi al-Kashir, a building resident, said his father, wife, five children, and two sisters were stuck for a time in the family's apartment -- trapped by thick smoke in the halls and terrified of gunmen at the building's entrance and on its roof.
"They tried to send ambulances, but the ambulances came under fire," he said.
Eventually, the fire was put out and the gunmen withdrew, security officials said. Medical officials said nine people were treated for smoke inhalation.
Throughout the day, the streets of central Gaza City echoed with the rattle of gunfire and were empty except for gunmen in black ski masks.
Frightened residents huddled in darkened homes after electricity to some neighborhoods was cut off by a downed power line. Buildings were pocked with bullet holes and windows were shattered by explosions.
"What is happening in Gaza endangers not only the unity government, but the Palestinian social fabric, the Palestinian cause, and the Palestinian strategy as a whole," said Saeb Erekat, a top aide to the Palestinian president.
Hamas official Ahmed Bahar, the deputy parliament speaker, called the fighting a major setback.
"We urge all the Palestinian parties to stop," he told the television station Al-Jazeera. "We urge them to direct our weapons to the Israeli enemy instead."
At nightfall, Hamas announced it would observe a unilateral cease-fire, and Abbas called on the warring parties to hold their fire. The United States, European Union, United Nations, and Arab League also called for a halt in fighting.
But truces declared the previous two nights failed to stick and battles raged well into the evening, killing two Hamas militants and a Fatah gunman.
Abbas planned to travel from his West Bank headquarters to the Gaza Strip today to meet with Palestinian Prime Minister Ismail Haniyeh of Hamas, said a presidential aide, Yasser Abed Rabbo.
One option for Abbas was declaring a state of emergency -- a step that would let him set up a small "emergency" government that could make decisions without parliament's approval and authorize a large deployment of security forces, Abed Rabbo said.
But it would be extremely difficult to carry out such a deployment, and Hamas said it would oppose an emergency government. "No party can impose itself on the other," Hamas spokesman Sami Abu Zuhri said.
Abbas spoke by phone yesterday morning with Hamas leader Khaled Mashaal, who lives in Damascus, Syria, and the two agreed to work to end the violence, government spokesman Mustafa Barghouti said.
Exiled Hamas official Moussa Abu Marzouk blamed the violence on the cutoff of international aid to the Palestinian Authority.
"The international community and Arab countries shoulder part of the responsibility for the current events, due to their attitudes toward the national unity government," Abu Marzouk told The Associated Press.
Hamas agreed to form the unity government with Fatah in the hope that the international community would end sanctions imposed on the previous Hamas-led government for Hamas's refusal to renounce violence and accept the existence of Israel.
Abbas, Fatah's moderate leader, is respected in the West but has been unable to lift the boycott.
According to Palestinian officials, yesterday's dead included the six Fatah bodyguards, five Fatah fighters, and three Hamas militants killed in gun battles.
Hamas forces also mistakenly killed five Hamas men in an ambush of a Fatah jeep carrying Hamas detainees. That attack also killed two Fatah men.
A nurse traveling in an ambulance was hit in the head by a bullet when she was caught in cross-fire, hospital officials said. Her family said she was brain-dead and on a respirator.
Yesterday afternoon a group of about 200 Palestinians marched through central Gaza City waving Palestinian flags and demanding an end to the fighting.
Dozens of masked gunmen used the cover of the demonstration to improve their positions on the street and then fired on the demonstrators, wounding eight people. The rest ran away.
Israeli ambulances stationed at the Gaza-Israel border transferred four Palestinian children who were badly injured to a hospital in southern Israel, according to Israeli rescue services.