The ruling Hamas group accused Palestinian President Mahmoud Abbas of Fatah of starting a war after his security forces opened fire on Friday on a Hamas rally in the West Bank and firefights broke out in Gaza.
"What a war Mahmoud Abbas you are launching, first against God, and then against Hamas," senior Hamas leader Khalil al-Hayya told a Gaza City rally of 100,000 Hamas supporters, who chanted "God is Greatest" and fired guns into the air.
At least 32 Hamas supporters in the West Bank city of Ramallah were wounded by gunfire from Abbas's forces, hospital officials said. Several were in critical condition.
Tensions were at their highest in a decade and followed months of failed talks to form a unity government between the ruling Hamas Islamist faction and Abbas's once-dominant Fatah.
Hayya said Hamas would not agree to holding an early election or a referendum on the issue, a move that Abbas could announce in a speech planned for Saturday in an attempt to break the political deadlock.
Hayya did not say what Hamas would do if Abbas made such a dramatic announcement.
The fresh violence broke out after Hamas, which controls the Palestinian Authority, accused a Fatah strongman and Abbas's presidential guard of trying to kill Prime Minister Ismail Haniyeh outside the Rafah border crossing with Egypt.
Although Israel was not involved in the latest fighting, its decision -- with US backing -- to prevent Haniyeh from entering Gaza with $35 million intensified the standoff in which Haniyeh's convoy came under fire late on Thursday.
"We know who opened fire (on Haniyeh's convoy) and they will be punished hard. From now on they will never relax and they will never sleep tight in their homes," said Hamas leader and Palestinian Foreign Minister Mahmoud al-Zahar.
One of Haniyeh's bodyguards was killed in the incident at Rafah on Thursday. Another bodyguard, the prime minister's son and a political adviser were wounded.
Hayya's comments were Hamas's strongest personal attack yet against Abbas.
Friday's fighting in the occupied West Bank was the fiercest since Hamas came to power in March after trouncing Fatah in January elections.
Outside Ramallah's main mosque, Hamas supporters taunted Abbas's security forces. "You look like Israeli soldiers. You are spies," they shouted.
Dressed in riot gear, the Fatah-dominated forces used clubs and rifle-butts to beat back the Hamas demonstrators before shooting broke out.
At about the same time, Hamas and Fatah forces in Gaza opened fire on each other on the streets. It was unclear if anyone was hurt.
Hamas spokesman Ismail Rudwan singled out by name Fatah strongman and lawmaker, Mohammed Dahlan, as being behind the shooting attack late on Thursday on Haniyeh's convoy as it was leaving the Rafah border crossing between Gaza and Egypt.
He called on Abbas to remove his presidential guard from the streets.
Dahlan said on Al Arabiya television that the accusations "are not worth answering".
He blamed Hamas "gangs" for the violence, which has surged since unidentified militants shot dead three young sons of an intelligence official loyal to Abbas outside the boys' school early this week.
"It (Hamas) is pouring oil on the fire," said Abdel-Hakim Awad, a spokesman for Fatah in Gaza.
Abbas still plans on Saturday to outline his options in the wake of months of failed talks with Hamas to form a unity government, Palestinian officials said.
Some Abbas aides say he might announce he has no choice but to call a referendum on elections, although he may not set any dates and leave the door open to fresh talks.
Abbas might also decide emotions are too high, and refrain from overt threats.
"Mohammed Dahlan bears the direct responsibility for the assassination attempt which targeted the prime minister and he bears responsibility for the blood of the martyrs in the incident," Rudwan told a news conference in Gaza.
Rudwan offered no evidence of Dahlan's involvement.