Also on Thursday, the widow of the British consul killed in one of the bombings appealed to the public for information.
Details about the investigation have been restricted by a court-ordered media blackout, but the daily Hurriyet, quoting security sources, said Abu Mussab al-Zarkawi, a Jordanian, was behind the two waves of suicide bombings that left 55 dead and nearly 750 injured in Istanbul.
Two car bombs exploded outside two Istanbul synagogues on 15 November and similar attacks on 20 November targeted the London-based HSBC bank offices and the British consulate, where the consul general Roger Short was killed.
His body was flown back to Britain in a Turkish military plane on Thursday and his widow, Victoria, issued a public appeal to anyone with information about the bombings or about those involved in carrying them out.
"Please come forward and help stop another outrage from happening in Turkey," she said in a statement issued by the British embassy in Ankara.
Officials here have said Turkish nationals linked to Islamist groups were behind the bombings that were claimed by the al-Qaida network and a local extremist group, the Islamist Great Eastern Raiders Front.
The bombings have led to at least one diplomatic spat.
Football-mad Turkey was angered by a decision by the footballing body UEFA to move three key European matches to other countries over security concerns.
Prime Minister Recep Tayyip Erdogan said he had cancelled a planned telephone call to British counterpart Tony Blair because of the latter's lack of support for keeping the matches in Turkey, Anatolia news agency reported.
"With Turkey being hit by terrorism on one side, we simply cannot accept that Europe hits us also (by taking away football matches)"
Turkish foreign minister
Erdogan has also been angered that the British Foreign Office warned publicly of the possibility of further bomb attacks in large Turkish cities.
Turkish Foreign Minister Abdullah Gul said that UEFA's decision was "unacceptable and would have to change".
"With Turkey being hit by terrorism on one side, we simply cannot accept that Europe hits us also," he said.
Hurriyet newspaper said Zarkawi leads an armed group called Hizbullah, based in mainly Kurdish southeast Turkey, and quoted security sources as saying he and his men had trained extensively in Afghanistan.
The group has no connection with the Lebanese Shia militia Hizb Allah.
A victim of the attack on the British consulate
Zarkawi is more widely known as the founder of al-Tawhid, an organisation trying to overthrow the Jordanian state and whose other stated aim is to kill all Jews.
Anatolia said that Turkish authorities had charged two more people late Thursday in connection with the attacks, bringing to 20 the number of people charged and held in custody.
The two were among a group of nine people sent to the state security court for questioning. The seven others were released.
Fifty-one people have now been detained and interrogated and 20 officially charged, most with belonging to or aiding an illegal organisation, which carries a maximum sentence of five years in prison.
The daily Aksam also reported that investigators had identified the suicide bomber at the HSBC offices, by matching his DNA with that of his brother.
It said his name was being kept secret because he was believed to have played "a key role" in the group he belonged to. The consulate bomber has been identified as Feridun Ugurlu.
At least two of the four suicide drivers came from Bingol - an impoverished town in mainly Kurdish southest Turkey - and police have examined computers and documents from an Internet cafe once run by a suspect.
The synagogue bombers have been identified as Mesut Cabuk and Gokhan Elaltuntas. Their suspected accomplice, Azad Ekinci, is still at large.