NEW YORK (AFP) - Police in the US city of Chicago on Wednesday denied a newspaper report alleging that they hold suspects illegally, beat them and deny them access to lawyers at a secret compound.

The Guardian report, which said activities at the warehouse echoed detention abuses in the US war on terror, follows protests over police tactics after the killing of a string of unarmed black suspects across the country in recent months.

The newspaper called the site an "off-the-books interrogation compound," and quoted a protester once held there and a former public defender as comparing it to a "CIA black site."

Detainees were beaten, resulting in head wounds, shackled for prolonged periods and held without legal counsel for 12 to 24 hours, including people as young as 15 years old, it said.

"At least one man was found unresponsive in a Homan Square 'interview room' and later pronounced dead," the Guardian wrote.

Chicago Police Department said Homan Square was one of a series of "sensitive" units but that it abides by "all laws, rules and guidelines pertaining to any interviews of suspects or witnesses."

"If lawyers have a client detained at Homan Square, just like any other facility, they are allowed to speak to and visit them," the department said in a statement.

"There are always records of anyone who is arrested by CPD, and this is not any different at Homan Square," it added.

The police said the warehouse also stores property, where members of the public claim inventoried items.

But the Guardian said its investigation showed that police detain people for hours without booking or posting public notifications of their whereabouts, preventing relatives knowing where they are.

In a follow-up story Wednesday, the Guardian quoted two former senior US justice department officials as saying that the allegations were disturbing enough to merit an investigation.