GAZA CITY, Gaza Strip – Violent clashes and mass protests erupted Saturday across the West Bank and Gaza Strip between followers of the militant group Hamas and Fatah rivals, after a Hamas leader accused Palestinian President Mahmoud Abbas of treachery.

The two sides traded gunfire and hurled stones and firebombs, escalating a fierce power struggle between militant and moderate factions over control of Palestinian security forces.

Abbas said Saturday he would not allow the accusations to plunge the Palestinians into civil war.

The unrest followed the president’s moves to take control of all six security forces, and Hamas’s response that it would form its own shadow army made up of militants and headed by a top fugitive that Israel has been hunting for years.

Abbas’ prompt veto of that plan provoked a scathing comment late Friday from ruling Hamas party’s political chief, Khaled Mashaal.

“We can understand that Israel and America are persecuting us, and seeking ways to besiege and starve us, but what about the sons of our people who are plotting against us, who are following a studied plan to make us fail,” Mashaal said from his base in Syria, without mentioning Abbas by name.

Fatah’s senior leaders promptly accused Mashaal of “igniting and preparing for civil war.” Tens of thousands of party loyalists took to the streets of the West Bank and Gaza Strip, protesting Mashaal’s remarks and demanding an apology.

Clashes were ugliest Saturday in Gaza City, where Hamas and Fatah followers traded gunfire and hurled grenades and firebombs. Hundreds of university students threw stones over the wall separating Hamas- and Fatah-run schools. Fifteen people were wounded, two seriously.

Later Saturday, hundreds of Fatah activists marched to Gaza’s Parliament compound, throwing stones and shattering windows in a government building.

Hamas’ refusal to disarm and recognize Israel has already cost it hundreds of millions of dollars in Western aid and Israeli transfer payments.