Gaza City Gaza Strip ? Rival gunmen exchanged fire Monday at two Gaza hospitals and Cabinet ministers fled their weekly meeting after the government headquarters was caught in the crossfire of a brutal day of infighting that killed 17 Palestinians.

The battles came a day after two militants from the rival Hamas and Fatah factions were dragged onto high-rise rooftops and thrown to their deaths in a power struggle that appears to be rapidly descending into all-out confrontation.

After sundown Monday, gunmen, apparently from Hamas, laid siege to the house of Jamal Abu al-Jediyan, the senior Fatah official in northern Gaza. They then dragged him outside and killed him, security officials said. Medics said he was hit by 45 bullets.

Al-Jediyan was a top aide to Gaza Fatah strongman Mohammed Dahlan and al-Jediyan’s brother was also killed, apparently in the same shootout.

Fatah spokesman Maher Mikdad harshly denounced the killing and threatened revenge.

“What is this, if not a war?” he said.

Fatah called on its members to target all Hamas political and military leaders.

The bloodiest clashes of the day took place in the northern Gaza town of Beit Hanoun. Fatah and Hamas gunmen exchanged fire near Beit Hanoun Hospital, killing a Hamas supporter. The battle then moved to the hospital, where three men from a Fatah-allied clan were shot dead.

At Gaza’s largest hospital, Shifa, combatants fired mortars, grenades and assault rifles.

Monday’s deaths brought to more than 80 the number of Palestinians killed since the latest round of infighting erupted in May. The violence overshadowed attempts to revive Israeli-Palestinian contacts.

Appeals for calm by the leaders of the two rival camps, President Mahmoud Abbas of Fatah and Prime Minister Ismail Haniyeh of Hamas, went unheeded. Repeated attempts to secure a cease-fire have failed.