Over 600 Egyptian children between the ages of 14 and 17 are being detained in a dilapidated underground prison near Cairo, it has been revealed.

The boys are being held in a prison connected to a police camp in Banha, a city 25 miles north of the Egyptian capital.

According to The Times, the teenagers are being held by Egypt's security forces on suspicion of offences such as joining groups designated as terror organisations by the Egyptian government and assaulting police officers.

It is claimed that they are being held in freezing cells with no access to sunlight or outdoors, with no visits from lawyers or relatives allowed.

"It's not legal to keep them there. According to Egyptian law, minors should be kept in juvenile detention," Halim Heneish, a human rights lawyer, told The Times.

"We are being barred proper access to them, the families and lawyers can only meet them during their detention renewal sessions."

Families of the teenagers held in the prisons accuse the security forces of torturing them when they were arrested and holding them without beds or blankets.

Radwan Ahmed, the father of 14-year-old son Mohammed who was arrested three months ago for blocking a road at a Cairo protest, told the newspaper that his son is being held with 25 people in one room at the prison.

"Dozens of policemen raided our home at 2am and took my son. They beat him and electrocuted him for several days," said Ahmed.

"The last time he saw me, he burst into tears. He looked thin and ill," he added.

Heneish also claimed that some of the teenagers held have contracted skin diseases after having to sleep for months without blankets in the damp prison cells.

Egypt's interior ministry denies that the prison exists and claims that all minors are held in acceptable juvenile detention facilities.