New York-based Human Rights Watch (HRW) said on Tuesday the men have been held for four months after security police started rounding them up for questioning about bombings at tourist resorts.
Many of the detainees, mostly Islamists, suspected Islamists or relatives of Islamists, have been tortured in detention and authorities have usually failed to tell their families where they are or what is happening to them, HRW said.
In informal meetings with Human Rights Watch, Egyptian officials justified the conduct of the police by saying the US and Israeli authorities behave in the same way when their security is threatened, HRW Director Joe Stork told a news conference where a report on the detentions was released.
Denial of torture
Challenged on the detentions and torture allegations at a meeting last month, Egyptian President Husni Mubarak said the reports were implausible because there were only a few thousand people in the whole of al-Arish, the capital of North Sinai province and the centre of the arrest campaign.
The bombings saw 34 people
killed and many more wounded
"President Mubarak's very dismissive remark ... betrays a certain arrogance that the president should better have kept to himself," Stork said.
Stork heads the Middle East and North Africa division of the human rights group.
Egyptian groups alerted the international rights community to the North Sinai arrests in December and Human Rights Watch sent a mission to the area to investigate.
The government has never confirmed or denied reports that police detained up to 3000 people in North Sinai after bombings in the east coast of the peninsula killed some 34 people in October.
At a meeting with Stork later on Tuesday, a senior Interior Ministry official said the police had detained only some 200 people in North Sinai, the HRW official told Reuters.
"I said I find that non-credible. He said: 'Bring us the names.' ... I can't say that I was very satisfied. I got denials that anything untoward was happening," Stork said, adding that he also met Major-General Ahmad Umar of the minister's office.
President Mubarak said he found
the detention figures implausible
The bombing targets were hotels and beach camps frequented by Israelis. The authorities said the mastermind was an al-Arish Palestinian who died accidentally in the bombing at the Hilton hotel in the border town of Taba.
The detention campaign does not fit well with the official version of the investigations, according to which all nine bombers and alleged accomplices are either dead or under arrest.
Asked how many people remain in detention, Stork said: "We don't really know and that's part of the problem - the utter, shameless failure of the government ... to respond to the needs of the families to know where their loved ones are."
"The estimate we made of 2400 people still in detention ... that's our best guess, based on what we do know," he added.
The 51-page report gave detailed first-person accounts of torture from named individuals.
Hamid Batrawi, 26, one of those later released, said he has hung for hours by his hands tied behind his back, beaten with a hose and given electric shocks every few minutes. He was taken to hospital unable to talk or walk.