NABLUS, West Bank -- A West Bank professor is thrown into a police jeep and beaten with pipes. Detainees in Gaza are prevented from seeing lawyers. Club-wielding troops in the West Bank break up a peaceful march, and their counterparts in Gaza keep journalists from covering a police raid.

It's all part of a widening crackdown on political opponents, both by the Western-backed Fatah movement in the West Bank and by the Islamic militant Hamas in Gaza.

The crackdown began after a July 25 beach-side bomb killed five Hamas militants in Gaza. Hamas blamed Western-backed Fatah and rounded up scores of Fatah activists in Gaza. Fatah-allied security forces in the West Bank responded by seizing dozens of Hamas supporters.

The U.S. and Europe have said little about violations in the West Bank, even as they're spending millions of dollars on police training to help lay the foundations of a democratic Palestine. The foreign trainers say the abuse isn't carried out by security forces under their supervision.

Both Hamas and Fatah portray the sweeps as security measures, and play down rights violations as isolated.

However, leading intellectuals in the West Bank told Palestinian Prime Minister Salam Fayyad last week that they're worried about diminishing liberties.

Since Hamas violently wrested control of Gaza from Fatah in June 2007, each side has been trying to assert control over its territory. Two human rights groups reported last month that as part of that effort, security forces in both territories systematically tortured detainees.

Analysts say a desire to prevent the West Bank from falling to Islamists appears to override other Western concerns.

"The West is supporting one Palestinian faction over the other. It's all about politics, not human rights," said George Giacaman, a political scientist from the West Bank's Bir Zeit University.

Despite the internal rifts, most Palestinians reject the idea of civil war, but the crackdowns raise the specter of armed conflict between the two sides. Palestinian President Mahmoud Abbas of Fatah's role in the escalating tension is cutting into his support.

Israel for its part has said that no peace agreement can be implemented until Gaza and the West Bank are reunited under Abbas' rule, but the reciprocal animosity is pushing that goal away.

In the meeting with Fayyad, Mamdouh al-Aker, head of The Independent Commission for Citizens' Rights, a Palestinian group, said "We have warned of (the West Bank government) turning into a security regime, and there are indications that we are heading in that direction."

Fayyad reminded participants of what he said was the danger posed by Hamas.

"As we all know, Hamas is not only working in Gaza," Fayyad said. "It works in the West Bank, too. Therefore, I cannot act as if nothing has happened."

The center of the West Bank crackdown is the city of Nablus, a former Hamas stronghold. Among those rounded up there included the acting mayor, several lawyers and prominent merchants suspected of helping Hamas.

Earlier this month, security forces seized four professors from the city's An-Najah university.

One of the professors, political scientist Raed Naerat, described himself as an independent but is portrayed by others as a sympathizer with Hamas' pragmatic wing. He said troops grabbed him two weeks ago, cuffed him, put a smelly sack over his head and bundled him into a jeep.

Naerat said he was driven around for almost four hours and beaten, including with metal pipes and rifles. He was held for two days, and doctors said he suffered bruises and a concussion from beatings.

Interior Minister Abdel Razak Yehiye, who oversees the West Bank security forces, said the detention of the professors was a mistake, and that he ordered them released. However, it is unlikely troops would act on their own in seizing respected members of the community.

The Palestinian security forces are also under pressure from Israel to assert control in once chaotic West Bank cities, as a condition for an eventual Israeli troop pullback. However, Israel says the Palestinian performance remains spotty, and that it's too soon to hand over security.

In recent weeks, Abbas' forces have become increasingly jittery.

They have targeted supporters of the Liberation Party, a pan-Islamic group whose supporters want to restore Islamic rule and criticize the West Bank's moderate leaders as "infidels."

In the past, Liberation Party activists were able to demonstrate freely, but recent marches were broken up. In the city of Hebron, Abbas troops beat photographers covering the march, and in the city of Ramallah, they prevented camera crews from filming as Liberation Party demonstrators were beaten with clubs.

Liberation Party activists say they espouse nonviolent change, but Palestinian security officials say they fear Hamas and other militants are using the fast-growing movement as a vehicle for dissent.

Political repression is also on the rise in Gaza.

Dozens of Fatah activists remain in detention, including district governors and intellectuals. Iyad Alami, a Gaza human rights activist, said lawyers have not been able to see detainees since the crackdown began.

A radio station linked to a small faction, the Popular Front for the Liberation of Palestine, was closed for three days. Hamas also banned the distribution of three daily newspapers produced in the West Bank.

Last week, Hamas imposed a closed military zone in the Gaza City neighborhood where Hamas forces had raided a Fatah-allied stronghold after hours of heavy fighting. The ban prevented photographers and camera crews from documenting often violent house-to-house searches. Several residents alleged that money, gold and computers were stolen by Hamas troops.

Fawzi Barhoum, a Hamas spokesman, said the complaints would be investigated, and claimed that the neighborhood was declared off limits to protect journalists from unexploded ammunition.

Associated Press writers Karin Laub and Diaa Hadid in Gaza City and Ali Daraghmeh in Nablus contributed to this report.

© 2008 The Associated Press