The organisers said the number of detainees could be as high as 18,000, although US forces have acknowledged only having more than 5,000. The figures are rising on repeated military sweeps against suspected coalition enemies.

"A lawyer is the most basic right," said one banner.

A woman whose three sons were arrested in October turned out with three of her grandchildren.

Amal Salim Madi, 65, said she had had no news about her sons and that the family was without any income.

"The Americans said they were taking them off for an hour of questioning. We have not seen them since."

"Why can't I send or receive a letter?" asked another banner.

Amal's sister, Laman Salim Madi, said her two sons were taken in August. She too had heard nothing since.

Uzma Bashir, one of the protest organisers and part of Iraq Occupation Watch, which groups anti-war bodies around the world, said the US practices showed a "pattern of real brutality".

Gene Stoltzfus, an American with the Chicago-based "Christian Peacemaker Teams (Getting in the Way)", said the attitude of the US authorities was "confusing".

"We try to see the prisoners, we follow case by case and sometimes we succeed." But he added that "the families are scared".

The group said Iraqi prisoners have been held for months by the coalition without legal defence, any contact with their families or any charges being brought.

Abu Gharib prison outside Baghdad holds some 10,000 Iraqi inmates, the Peacemaker Teams said, adding that detention centres have been built in most US bases in Iraq.

Since the International Committee of the Red Cross left Baghdad in October after a bomb hit their offices, prisoner visits have to be organised from Jordan and have thus become less frequent.

Meanwhile, more attacks can be expected during the next six months leading up to Iraq's independence and the US military response will be sharper, US civilian administrator Paul Bremer told The New York Times.

"We'll have bad days and good days," Bremer said in an interview published yesterday.

On the type of relationship the Iraqis and US military might strike up when a status of forces agreement is drawn up by March 15, Bremer said it would likely be based on security conditions in Iraq.

"It's a question that really ought to be asked in six months," he said. "My own guess is we're going to have an increase in violence over the next six months."

As Iraq advances toward a democratic government and sovereignty, Bremer and US military commanders believe terrorists and people loyal to the fallen dictatorship of Saddam Hussein will step up their attacks on coalition forces.

"The violence will be precisely because of the fact that we're building momentum toward success," Bremer said.

Bremer was echoing a warning issued Sunday by top coalition commander in Iraq, Lieutentant General Ricardo Sanchez: "We expect to see an increase in violence as we move towards the transfer of sovereignty at the end of June."

The spike in violence, Bremer said, will be met by a sharper military response and an increased American investment in improving the daily lives of Irqis.

"As we respond to attacks -- and we do have to respond to attacks to show that we mean to carry out our security obligations here -- we have to be careful that we don't overdo that," he said.

"We balance that by putting an enormous amount of money into reconstruction efforts," he said, adding that he wanted to double the estimated 100 million dollars already invested in projects in provinces under US control.