The Islamic militant group Hamas on Friday said it was suspending talks with the rival Fatah movement on forming a coalition government after 14 people were killed in new infighting.

"Following the awful massacres committed today in Gaza and northern Gaza ... we have decided to postpone all dialogue with Fatah," said Ismail Radwan, a Hamas spokesman.

Earlier, Fatah also said it was suspending negotiations. The two sides have been trying to form a coalition government to end a year-old political impasse.

The fighting was among the deadliest in nearly two months and marred the first anniversary of Hamas' upset victory in Palestinian elections. After nightfall, the fighting showed no signs of slowing, as the sound of gunfire echoed throughout Gaza City.

The heaviest shooting was concentrated around the home of Mansour Shaleil, a local Fatah leader in the Jebaliya refugee camp just north of Gaza City.

Hamas gunmen surrounded the home early Friday to detain Shaleil, accusing him of involvement in a shooting that killed two Hamas supporters. After an hours-long standoff, dozens of Hamas gunmen stormed the house and exchanged fire with Shaleil and his supporter, according to witnesses and ambulance drivers.

They later withdrew, Palestinian media reported, leaving Shaliel unharmed. Two people were killed.

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"It looks like they forgot who the enemy is," said Maher Mekdad, a Fatah spokesman. "They forgot the Israeli occupation."

Fatah gunmen, meanwhile, kidnapped 19 Hamas militants and threatened to kill them if Shaleil was harmed, officials on both sides said.

During the day, fighting also spread to the headquarters of the pro-Fatah Preventive Security agency in Gaza City. Four Hamas gunmen were killed in a battle outside a nearby mosque. Hamas accused Fatah gunmen of starting the battle and wounding several worshippers in a drive-by attack. Mortar shells and rocket-propelled grenades were fired during the melee, smashing windows on several homes.

In other incidents, fighting erupted outside the residences of Palestinian President Mahmoud Abbas of Fatah and Foreign Minister Mahmoud Zahar of Hamas. Hamas officials said Zahar's home was damaged by two rocket-propelled grenades.

Hundreds of security forces loyal to Abbas — who was in Europe at the time — were sent into the streets to protect his compound and various security installations.

In all, 14 people were killed throughout Gaza, medical officials said, including a 2-year-old boy who was shot while traveling in a car in the southern town of Khan Younis. Hamas and Fatah officials accused each other of firing the deadly shot.

Tensions have been high since Hamas swept parliamentary elections in January 2006, ending four decades of Fatah rule. Those tensions have frequently erupted into violence, killing some 15 people in Gaza since early December.

Hamas promised to root out corruption and improve social services. But the Hamas-led government has been paralyzed by an international boycott and accomplished little on its agenda.

Israel and Western donors have cut off hundreds of millions of dollars in funding to the Palestinian government, demanding Hamas renounce violence and recognize Israel's right to exist. Hamas has rejected the conditions, despite deepening poverty in the West Bank and Gaza caused by the sanctions.

After praying at a mosque in Gaza City, Haniyeh spoke proudly of the Palestinians' refusal to succumb to the international sanctions.

"The siege has become ineffective," he told reporters. "The Palestinian people were patient and steadfast in the face of this siege, as was their government, and we have not offered any concessions."

Seeking a way out of the crisis, Abbas has called on Hamas to join Fatah in a moderate coalition government. Abbas, who was elected separately, hopes a moderate platform will get the sanctions lifted and allow him to restart peace talks with Israel.

Abbas has threatened to order early elections, but Hamas has said it would boycott a new vote. Abbas' threat to call new elections, along with the deadlock in unity talks, has fueled the factional violence.