By Martin Patience
BBC News, Ramallah
Evidence of a crackdown on Hamas supporters is easy to see
Three military jeeps and more than 20 armed members of the Palestinian security forces surrounded Fouad Frokh's family home in the early hours of the morning.
The Fatah-affiliated forces demanded to know the whereabouts of Fouad's father and then searched the house for weapons.
When they turned up nothing - no father, no weapons - they "arrested" Fouad's 16- and 18-year-old brothers.
"They really wanted my father," said Mr Frokh, 23, a video editor. "They thought because he's got a beard and goes to the mosque a lot that he is a Hamas supporter."
With Hamas taking almost complete control of Gaza after battling Fatah forces, there is growing fear in the West Bank that retribution will be meted out against the Islamic movement's supporters.
Gaza is a Hamas stronghold but the West Bank is Fatah territory.
Hamas, an Islamic organisation, rose to prominence in Gaza during two Palestinian uprisings and refuses to recognise or negotiate with Israel.
Fatah, a secular political grouping headed by President Mahmoud Abbas, ran the Palestinian Authority until 2006 and officially recognises the Jewish state.
The raid on the Frokh family home was one of dozens carried out by Fatah-affiliated security forces across the West Bank in the past 24 hours.
In the city of Nablus, dozens of gunmen set fire to the third-floor office of several Hamas members of parliament.
In Ramallah, almost all Hamas politicians and prominent supporters have either fled or gone into hiding.
While Mr Abbas is urging restraint among his security forces, many members want to avenge the events in Gaza.
One police commander in Ramallah said that when some of his colleagues hear that a Hamas member has been arrested or kidnapped "they hope that he will be killed".
For politicians and analysts there is a real concern that the violence that has torn Gaza will spill over into the West Bank - but this time Fatah will be expected to have the upper hand.
"I believe that the violence could spread like wildfire in the West Bank," said Shadi Manassra, an editor at the Palestinian newspaper al-Hayit Jeeda.
Residents are urging restraint between Hamas and Fatah
Evidence of a crackdown on known Hamas supporters is easy to see.
I stood at one street corner as security forces bundled the owner of a bookstore selling a Hamas newspaper, al-Risala, and Islamic books into the back of a vehicle.
The jeep then tried to speed off through the milling crowd.
Further up the street stands the Jamal Abed Nasser mosque, known to be popular among Hamas supporters.
But none of the worshippers at afternoon prayers said they had any affiliation with the Islamic movement.
Spilling onto the street where hawkers sell nuts and pears, shoes and shirts, the men all denounced the violence in Gaza.
"This is all the work of Israeli hands," said one.
"God will decide what happens," said another.
One woman stood at the mosque's entrance, hysterically calling for the mosque's imam, the prayer leader, to meet her.
She wanted him to deliver an impassioned plea urging restraint in the West Bank between supporters of Hamas and Fatah.
But her request went unanswered.