Hamburg, Germany (CNN) -- Ahmed Sidiqi, the man allegedly at the heart of an al Qaeda plot to target European cities, was detained by a group of unidentified men in Afghanistan three months ago, his family has told CNN.
German intelligence officials say Sidiqi was arrested in Kabul, Afghanistan, in July and has been held at the U.S. airbase at Bagram ever since. They say he has provided detailed information about an al Qaeda plot to carry out Mumbai-style attacks against several European cities. He has not been charged.
Sidiqi's father, Mohammed Naim, said his son was on his way to the German embassy in the Afghan capital to get a new passport when he was detained.
"It was a question of him having lost his passport or having had it stolen, he said," Naim told CNN.
Sidiqi had contacted his family in Hamburg from Kabul shortly before his arrest to tell them he missed them greatly and planned to come home soon, his sister said. She described Sidiqi as a devout family-loving man.
Sidiqi's sister, who asked that her first name not be used, told CNN that she cannot remember exactly when he made the call home but it was around June.
When he set off for the German embassy, Sidiqi told his wife to wait for him at their residence in Kabul. But according to Sidiqi's father, he never returned. Instead, Sidiqi was apprehended by a group of men who placed a black hood on his head and bundled him away, says his father.
His father says he received information on his son's arrest through contacts in Kabul who had spoken with his Sidiqi's wife. Eyewitnesses included an Afghan youth who said he saw Sidiqi being led away with a hood over his head, according to the father.
Sidiqi's father says he does not believe allegations that his son is at the heart of an al Qaeda conspiracy. "My son is not a killer, he's just not capable of that," he told CNN, stressing that such acts are absolutely forbidden in Islam. Sidiqi's sister says she too is shocked by the allegations.
According to Sidiqi's sister, her brother left Hamburg last year to start a new life in Afghanistan with his wife, an Indonesian citizen. She says that financial problems in Hamburg, including difficulty paying his rent, contributed to his decision to leave. "He had some debts and he was determined to earn money in Afghanistan to repay them," his father told CNN.
According to German intelligence agencies Sidiqi had a job cleaning aircraft at Hamburg international airport before leaving for Pakistan. Sidiqi's father said he also did some work in Germany related to computers.
Before setting off, Sidiqi told his family he was going to meet some friends in Pakistan and then go across from there to Afghanistan, according to his sister. In later phone calls he would not reveal his location, according to his father.
Sidiqi's sister confirmed he had attended the Taiba mosque in Hamburg, where several of the 9/11 conspirators met.
German intelligence agencies say that Sidiqi set off from Hamburg with ten other individuals from the mosque in March 2009 to join up with a militant group fighting Jihad against American troops in Afghanistan. They say that Sidiqi had been on their radar because of his links to radical extremists. Sidiqi, they say, first came to Germany from Afghanistan with his family in the early 1990s.
"He was someone very well known to us," a senior German intelligence source told CNN, "and we had him under heavy observation since 9/11."
Sidiqi, according to German intelligence officials, moved in the same circle as Mohammed Atta, the lead hijacker in the 9/11 attacks, who lived in Hamburg in the late 1990s.
Sidiqi's father says an official from the International Committee of the Red Cross recently visited the family with a letter from their son. In it, Ahmed said he was okay and that he hoped to return home soon, according to his father. There was no allegation of mistreatment. Nevertheless Sidiqi's family say they are very concerned about how their son is being treated.