Newspapers reported on Monday that the man was arrested last week near the Iranian border.
His arrest marks a step forward for Turkish authorities who were originally caught flat-footed by the wave of lethal explosions.
Police said the suspect used the cover of a detergent factory in Istanbul to make the explosives used in the four car bomb attacks on British and Jewish targets.
"When I went to Afghanistan in 1994 I was trained in combat techniques and bombmaking at a camp under the control of al-Qaida," the Milliyet newspaper quoted the man as telling Turkish investigators.
Bin Laden order
And the Hurriyet newspaper quoted him as saying: "The order for the attack came personally from Usama bin Laden through two men who went to Afghanistan."
The suicide blasts on 15 and 20 November hit the British consulate, the offices of the HSBC bank and two synagogues in Istanbul.
"When I went to Afghanistan in 1994 I was trained in combat techniques and bombmaking at a camp under the control of al-Qaida"
Milliyet newspaper quoting a Istanbul bombings suspect
The majority of the dead were Muslim Turks, most of them passers-by.
"I was criticised within the organisation because so many Muslims died," the suspect told authorities, according to the Sabah newspaper.
The reports said the targets were not those originally chosen by al-Qaida, but had been changed during the planning process.
Human rights abuses
Turkish authorities have arrested about 30 people in their investigation into the bombings, but a number of suspected ringleaders remain at large.
However, human rights groups have often accused Turkey of using newspapers as a conduit for false information.
In a 2003 rights' report on Iraq, Amnesty International said many Turkish citizens faced imprisonment or harassment, simply for expressing Islamist views.
The report added that torture in custody remained widespread and was practised systematically in many police stations.