LONDON, England (CNN) -- Saudi Arabia's campaign against the al Qaeda terrorist network has led to "massive human rights violations" by security forces, including torture and the arrests of non-violent reformists, the human rights group Amnesty International reported Tuesday.
The group estimates about 3,000 people are being held without charges, sometimes for years and without access to lawyers, after being swept up in a clampdown that began in 2003.
"There is no doubt that the leading violator of human rights in Saudi Arabia are the security forces, under the leadership and control of the minister of interior," said Lamri Chirouf, an Amnesty International researcher and the lead author of the report.
Without open trials and due process, "it's difficult to say whether those actually who committed the crimes that we are talking about are being punished," he said.
Though Saudi law and international treaties prohibit the use of torture, the report states: "Courts readily accept 'confessions' which defendants allege they were forced to make under beatings, electric shock torture or other ill-treatment."
Saudi authorities "show no interest in investigating such allegations and bringing to justice those who perpetrate torture or who order or acquiesce in its use," the report states.
Neither Saudi officials in Riyadh nor at the kingdom's embassy in London would respond to requests for comment on the report. But one Saudi source told CNN the report was flawed, and that the results of the crackdown speak for themselves.
Al Qaeda launched a wave of attacks on government buildings, oil installations and international contractors in Saudi Arabia in 2003. The Islamic fundamentalist movement supports the overthrow of the Saudi monarchy and carried out the September 11, 2001, attacks in the United States, the kingdom's leading ally.
The Saudis responded with thousands of arrests and in some cases, fought gun battles with militants in Riyadh and other cities.
The last major attack in Saudi Arabia took place in 2005. In early July, the Saudis announced that 323 people had been convicted and seven acquitted after trials that were closed to observers.
Those convicted will serve prison terms ranging from a few months to 30 years, the official Saudi Press Agency announced.
Saudi Arabia's King Abdullah has taken tentative steps to liberalize the country since coming to power in 2005, including establishing human rights commissions that work with international agencies, and barring detention without trial for more than six months.
But those efforts "have been totally undermined by the harsh measures of fighting terrorism," Chirouf said.
"These are basic rights of people that should not be violated by anybody, and should not be made a political football in the struggle for power or positions," he said.
In many cases, he said, those arrested appear to have been targeted for their criticism of the government -- including reformist blogger Fouad al-Farhan, who was jailed in late 2007. Amnesty said its information suggests al-Farhan was arrested for blogging about Saudi reformers who themselves were jailed without charge.
"He had not said anything that amounted to a criminal offense in the sense of international human rights standards," Chirouf told CNN. "For that, he spent a long time in detention, solitary confinement, without trial or anything."
Al-Farhan was released without explanation in April 2008, after five months in custody. At the time, Maj. Gen. Mansour Al-Turki an Interior Ministry spokesman, said the case "is not related to the government, is not related to the Ministry of the Interior or to the police or to the security situation."