An international human rights group has accused the European Union's border control agency of knowingly exposing migrants to “inhuman and degrading” conditions.

In a report entitled “The EU's Dirty Hands,” Human Rights Watch said Wednesday that the agency known as Frontex takes the migrants to Greek detention centers known for inhumane conditions, and thereby shares responsibility for human rights violations.

During its investigation, the New York-based advocacy group found a crowded detention center where unaccompanied children were placed with unrelated adults of both sexes in cells where sewage ran on the floor.

The European Commission rejected placing blame on Frontex for conditions in Greek detention centers. While admitting that the unacceptable state of the detention centers is well known, EU spokeswoman Michele Cercone says Greek authorities alone must bear the responsibility.

In a related development Wednesday, migrants clashed with Italian police and residents on the tiny Island of Lampedusa during a protest at an overcrowded holding center. Television footage showed riot police beating migrants with clubs, forcing many to jump from a balcony to escape the blows. The clashes came a day after the migrants, facing forced repatriation, set the overcrowded facility on fire.

More than 50,000 migrants, many fleeing unrest in Libya, Tunisia and elsewhere in North Africa, have arrived on Lampedusa since the beginning of the year. The island, Italy's southern-most point, is the biggest gateway for illegal immigration into the European Union. Residents have complained they are being overwhelmed.