The deep division between the Hamas and Fatah parties is not only confined to the Palestinian political arena.

It often comes much closer to home, dividing families.

Ahmad and Hamid know how that feels.

They are brothers, and both rising figures in their local political scene. But one is climbing the ranks of Fatah, and the other, Hamas.

The great Palestinian party political fault line runs through the home they share.

They live in a village near the West Bank city of Nablus, and these are difficult, sometimes dangerous, times for the area's Hamas supporters. The West Bank is Fatah's stronghold, and the brothers had insisted on changing their names so that they could speak frankly.

As they began to talk, it became clear how badly politics and personal relationships have become entangled in the village.

"My brother was arrested by security agents who came to the house," said Ahmed, the Fatah supporter. "And some of them were relatives and even friends of his."

Family first

He spoke of how hard it had been to watch Hamid being taken away "by security forces that are meant to protect us".

But the Hamas man bore no grudge towards his brother. Hamid said Ahmad had done all he could to use his influence in Fatah to get him freed.

"This is something positive - testimony to the traditions and principles that we were brought up on," he said. "Our parents drilled into our characters that family comes first, no matter what."

And both of them were able to joke about their divided allegiances.

"We try to focus on what we have in common - not our differences," said Hamid.

And certainly they share a loathing of Israel.

As they began to speak, the occupation was almost literally in the air they breathed.

You could hear the roar of an army helicopter filling the night as it circled in the darkness somewhere above the valley.

And on the hill just up from their home sat the lights of an Israeli settlement.

The great difference between the two parties that the brothers have joined is how best to confront the occupation.

Fatah's leaders believe it may still be possible to negotiate an end to it, and set up a Palestinian state alongside Israel.

Hamas takes a much harder line. It refuses to renounce violence, and although it says it is willing to consider a protracted truce, its charter still talks of seeking Israel's destruction.

Personal differences and other factors have further soured the atmosphere between the factions for many years. But the tensions became extreme after Hamas fighters routed Fatah in Gaza in 2007.

Both the brothers in the village had served time in an Israeli jail.

But Hamid, the Hamas man, has also spent several months altogether over the past two years locked up by his own people - the Fatah-dominated Palestinian security forces.

He said the guilt that his guards felt showed in their eyes.

There were even men he had actually done time with in prison in Israel who later became his jailers in the West Bank.

Human rights

The Palestinian Authority's commander in charge of security in Nablus is General Khair Ali - a veteran of the war in Lebanon and a man who spent decades in Fatah's military ranks.

He denied that there were any political prisoners in the area.

He said that all those detained were arrested in connection with the possession of weapons or involvement in outlawed military activity of some kind.

But the Palestinian Independent Commission for Human Rights says it has heard of hundreds of cases of illegal detentions across the northern West Bank this year alone.

It's concerned, too, about many reports of mistreatment and torture, and three deaths in custody.

And the Commission's director, Randa Siniora linked the situation to the fraught political climate.

She said that the security forces were exaggerating the threat that Hamas might pose.

It is worth bearing in mind too that candidates on a Hamas-backed list actually won the last municipal and parliamentary elections. They dominate Nablus city council.

But the United States and Europe heavily support the real power in the West Bank: the Fatah-backed authorities. And there will be those who argue that this is another example in the Middle East of Western powers being prepared to overlook concerns about human rights and democracy in order to assist an ally that is tough on radical Islamist elements.

For its part, Hamas's human rights record in its stronghold, Gaza, is every bit as dire as that of Fatah in the West Bank.

Hamas's conduct during and after the Israeli attack on Gaza earlier this year was condemned in a report by the New York-based organisation, Human Rights Watch.

"Hamas moved violently against its political opponents and those deemed collaborators with Israeli forces," the group said. "The unlawful arrests, torture and killings in detention continued even after the fighting stopped, mocking Hamas's claims to uphold the law."

Human Rights Watch said Hamas had targeted Fatah members, especially those who had worked in the Fatah-run security services.

"The widespread practice of maiming people by shooting them in the legs is of particular concern," said the report.

While Hamas and Fatah continue to tear at one another, many Palestinians look on in despair. Their view was summed up by a Nablus city councillor, Hafez Shaheen.

He said that the political feud had set the Palestinian cause back by several years.

With both parties trying to uproot each other in their respective strongholds, he said only the Israelis would benefit.