Western intelligence agencies have told the BBC that Ali Abdul Rahman al-Ghamdi, recently taken into custody, is al-Qaeda's top leader in Saudi Arabia.
Little is known about Ghamdi's early life
Mr Ghamdi, suspected of masterminding the deadly May bombings in Riyadh, has been linked to several senior leaders of Osama Bin Laden's al-Qaeda network.
He is also said to have been in Afghanistan during the US-led conflict in the country in 2001.
A US official has told the BBC that the detention was a major blow to the al-Qaeda network.
Very little is known about his early life and on Friday, Saudi newspapers published his brief biography.
They said he was born in 1974 in the southern Saudi province of Baha, married a Moroccan woman and became a student of Islamic theology.
He studied in both in Saudi Arabia and Afghanistan; learning the entire Koran by heart.
The al-Riyadh newspaper said Mr Ghamdi had spent years fighting in Chechnya and Afghanistan.
A US official told Reuters news agency that he is believed to have been fighting on the frontlines in Afghanistan during the US-led conflict there.
He was also present for the beginning of the battle for the cave compound at Tora Bora in late 2001 - where Osama Bin Laden is alleged to have hidden - but left just before the heavy bombing began, the official said.
US officials say he has been linked to Saif al-Adel and Abu Mohammed al-Masri, two of the most senior al-Qaeda operatives who remain at large, the Associated Press news agency reported.
It is thought the pair have been in hiding in Iran.
He is also thought to be an associate of Khalid Sheikh Mohammed, accused by the US of having planned the 11 September attacks.
Saudi officials said that Mr Ghamdi surrendered to them though his reasons for doing so are not clear.
BBC correspondent Magdi Abdelhadi says that it seems his tribe came under pressure to assist in the search for him.
Mr Ghamdi's father, when interviewed, told Saudi Arabia's al-Riyadh newspaper he was pleased his son had apparently surrendered.
"Thank God my son has given himself up because this has made me
at ease and pleased all his family members," he said.
"This is the correct thing to do and something he should have done long ago."