The city centre's transformation into a combat zone happened with little overt warning. On Saturday, shoppers darted peacefully through bustling downtown markets.
But early on Tuesday the Palestinian Authority's security forces carried out a rare operation to arrest a prominent member of the Islamist group Hamas, Moussab Shtayyeh, enraging many in Nablus, who accuse the PA of being Israeli pawns and tacitly accepting the occupation of the West Bank.
Shortly after the arrest, central Nablus was a no-go zone. Youths hurled stones at PA armoured trucks and lit fires on the streets as the sound of gunfire rang through the city.
AFP spoke to several people in Nablus, most of whom requested anonymity, fearing retribution if they criticised the PA and its 87-year-old president Mahmud Abbas, whose popularity in the West Bank has slumped to historic lows.
"There is tension because of Moussab Shtayyeh's arrest by the Palestinian forces and we are targeting them because they are coordinating with the Israeli occupation forces," said Hamza, a young man in his 20s.
A young Palestinian journalist, who declined to give his name, said that beyond Shtayyeh's arrest, "deeper" factors had fuelled Tuesday's violence.
He said the young people fighting the PA were not linked to the Islamist groups Hamas or Islamic Jihad, nor were they disenchanted members of Abbas's secular Fatah movement.
"They are young Palestinians, part of a new generation that isn't under anyone's thumb who are angry at both Israel and the Palestinian Authority."
'The Lion of Nablus'
The northern West Bank has seen near daily unrest in recent months but that has typically involved Israeli occupation army and Palestinian fighters.
Israel has conducted hundreds of raids in the occupied West Bank since March, pursuing militants it accuses of involvement in a spate of deadly attacks on Israelis.
Dozens of Palestinians have been killed in the Israeli raids that have hit several towns and cities, including Nablus and especially nearby Jenin, a historic militant stronghold.
Among those killed was an 18-year-old fighter named Ibrahim al-Nabulsi, who since his death in August has become a social media folk hero, nicknamed the "Lion of Nablus".
An image of him -- with his square jaw, black beard and assault rifle in his hand -- adorns pendants on sale at Nablus markets, and his picture is pasted on the windshields of scooters buzzing through the city.
His mother Huda, her head wrapped in a pure white scarf surrounded by pictures of her late son, said "when he was younger, Ibrahim was gentle."
"He loved design," she said. "But the injustice that surrounded him brought him to the other side."
His father Alaa said the relentless Israeli raids on their communities made young Palestinians feel abandoned by the PA.
"The young generation is not crazy but they grew up under the occupation, all they know is raids and injustice and it has left them deeply angry," he said.
"The increase in Israeli raids in Jenin and Nablus weakens the Palestinian Authority and creates further distance between the PA and the population," he told AFP, avoiding direct criticism of the Palestinian president.
It was not immediately clear why the PA moved to arrest Shtayyeh and Amid Tbaileh, another Hamas member detained with him.
But Israel regularly calls on the PA to take firmer action in areas of the West Bank nominally under its control, notably cities like Nablus.
Last week, after two Palestinians and an Israeli soldier were killed in clashes near Jenin, Israeli Prime Minister Yair Lapid said he would "not hesitate to act in any place that the Palestinian Authority does not maintain order".
Writing in the Israeli newspaper Maariv, leading security commentator Alon Ben David said the flurry of army raids had "further eroded the challenged status of the Palestinian Authority", with conditions ripe for a new intifada, or uprising, like those of 1987 to 1991 and 2000 to 2005.
"Israeli officials have been talking for years about the need to prepare for the day after Abu Mazen (Abbas)... but practically speaking that day is already here," he said, arguing that the president's authority is minimal and succession battles are already brewing.
The mix of intra-Palestinian violence and anti-Israeli resentment "is liable to turn into a new Palestinian intifada that is growing before our eyes, Intifada 3.0," he said.