The father of Mohammed Atta, the alleged ringleader of the September 11 attacks, said in an interview published yesterday that his son was still alive.

"He is hiding in a secret place so as not to be murdered by the US secret services," Mohammed el-Amir Atta, 66, told the German newspaper Bild am Sonntag. He also vehemently denied that his son - believed to have flown the first plane into the World Trade Centre - had taken part in the atrocities, blaming them instead on "American Christians".

The interview painted a picture of a tortured man who has not come to terms with his 33-year-old son's death or with the huge crime laid at his door. He said he feared the US would try to poison him.

Speaking from his Cairo home, Mr Atta described hearing about the attacks after returning from a holiday on the Red Sea on the evening of September 12. "My daughter called and said she was going to drop in. She stood at the door and said 'turn on the TV'," he said. Amid images of the jets crashing into the Twin Towers, he saw his son's passport photograph.

"As I saw the picture of my son," he said, "I knew that he hadn't done it. My son called me the day after the attacks on September 12 at around midday. We spoke for two minutes about this and that.

"He didn't tell me where he was calling from. At that time neither of us knew anything about the attacks."

Mr Atta said he did not condone the attacks, but could understand the hijackers' motivation. "Every day our Palestinian brothers are being murdered, their houses destroyed. If their relatives were to fly a plane into the Empire State Building I couldn't hold it against them," he added.

Mr Atta called his son a "gentle and tender boy", who enjoyed reading history and geography books and was nicknamed "Bolbol", or nightingale, by his parents.