Two human rights groups on Monday decried widespread mistreatment and torture in Palestinian jails - an issue taking on fresh urgency with a flare-up of Hamas-Fatah violence over the weekend in the Gaza Strip. The groups' reports looked at human rights violations during the past year, since Hamas wrested control of Gaza from the forces of Palestinian Authority President Mahmoud Abbas. In the past year, the security forces in both the West Bank and Gaza have carried out large-scale, arbitrary arrests of political opponents, the Palestinian human rights group Al Haq said in an 85-page report. More than 1,000 people were detained by each side, Al Haq estimated, even before a roundup of some 200 Fatah supporters in Gaza over the weekend, following a bombing that killed five Hamas members. An estimated 20 to 30 percent of the detainees suffered torture, including severe beatings and being tied up in painful positions, said Al Haq director Shawan Jabarin, citing sworn statements from 150 detainees. "The use of torture is dramatically up," added Fred Abrahams, a senior researcher for Human Rights Watch, a US-based group that is releasing its own report on abuse later this week. Human Rights Watch said Abbas's forces need to come under closer scrutiny because of the massive international support they enjoy. "The international community has pledged $8 billion to the Palestinian Authority in the West Bank and that gives them a heavy responsibility to make sure the security forces don't use torture and respect human rights," said Abrahams. Funding of Abbas's forces should be linked to an improvement in the human rights record, Human Rights Watch said. PA Prime Minister Salaam Fayad acknowledged "shortcomings," but said human rights violations have decreased. "I'm not defending anyone, but I can assure you that we have treated flaws and don't allow violations. The upcoming reports will be better," Fayyad said. In Gaza, Hamas spokesman Fawzi Barhoum accused the Fayad government of trying to destroy Hamas in the West Bank with US backing. Barhoum acknowledged "mistakes" were made by the Hamas forces, but said that unlike in the West Bank, violators were increasingly punished. The Al Haq report described a series of methods used by interrogators in both territories. Commonly, detainees' heads were covered by sacks. They'd have their hands tied behind their backs and were made to stand for long hours. Those who moved risked beatings on arms, legs and the soles of feet. Other methods included threats, humiliation and isolation in tiny cells. Three ex-detainees - two from the West Bank village of Salem and one from Gaza - gave similar accounts to AP. Majdi Jabour, a 33-year-old construction worker, said he was detained on Nov. 17 by Military Intelligence in the city of Nablus, near Salem. He said interrogators demanded to know where he had hidden the automatic rifle of his late brother, a member of the Hamas military wing killed by Israel in 2002. Jabour said he insisted he had no ties to Hamas and did not know of a weapon. He said that for the next six days, he was beaten severely with sticks and fists, including on the soles of his feet. His legs became so swollen and his feet so sore that he couldn't stand up, he said. He was also forced to kneel on glasses placed upside down on the floor and made to stand in the cold winter rain for hours. Jabour said he was taken to Nablus's Rafidiyeh Hospital after an interrogator rammed a screwdriver into his back, making him pass out. Another man from Jabour's village, 50-year-old Hosni Jabara, said he was arrested by the Preventive Security Service in Nablus on Jan. 28, and was tied up in painful positions off and on for 32 days. At times, he was pulled off the ground by a rope hanging from the ceiling and attached to his hands tied behind his back, said Jabara. In Gaza, a Fatah supporter said he was seized by Hamas security and beaten severely for several hours this spring, until he lost consciousness and had blood streaming down his face. The man in his early 30s showed a photo of what he said were his black and blue buttocks. After initially agreeing to be quoted and photographed, he withdrew permission, saying he had received new threats from Hamas. Al Haq described the mistreatment as systematic. In the West Bank, most of the abuse was carried out by the Preventive Security Service and the General Intelligence, the rights group said. In Gaza, the lead was taken by Izzedine al Qassam, the Hamas military wing which has been folded into the security forces, according to Al Haq. The group said it had confirmed two deaths in detention, one in Gaza last July and one in the West Bank in February. Al Haq said it noted a decline in West Bank abuses in the past three months.