The investigation into the deadly suicide bombings in Istanbul took a major step forward yesterday when Syria handed over 22 Turkish suspects wanted over the attacks, officials said.

The handover brings to nearly 60 those in custody in Turkey over the quadruple suicide attacks November 15 and 20, in which truck bombs at two synagogues, a British bank and the British consulate killed 61 people including the bombers.

The Turkish suspects handed over by Syria were believed to be connected with a man who allegedly played a key role in the attacks, a police statement quoted by Anatolia news agency said.

It named the man as Azat Ekinci, adding that the agreement to hand over the men was part of an anti-terrorist deal between Ankara and Damascus.

Ties between Damascus and Ankara have in the past been tense because Syria for a long time gave refuge to Kurdish separatist leader Abdullah Ocalan, but expelled him at the end of 1998.

Ocalan, arrested two months later, is now jailed for life in Turkey.

The governor of the province of Hatay, Abdulkadir Sari, told the Turkish NTV news channel that two of the suspects were close to Ekinci.

Another 21 people have already been charged and are currently being held over the bombings of the Jewish and British targets, attacks claimed by al-Qaeda and a local extremist group, the Islamist Great Eastern Raiders Front (IBDA-C).

Sixteen others are being questioned by anti-terrorism units, according to Istanbul governor Muammer Guler.

Police have also identified the fourth and final suicide bomber - the man who blew himself up outside the offices of British-based banking giant HSBC.

Anatolia quoted Guler as saying the suicide bomber was an Ankara resident born in 1956 by the name of Ilyas Kuncak.

The agency had earlier reported that the man - whose remains were analysed at the Istanbul Forensic Medicine Institute and compared with the DNA of his relatives - had been identified as Mevlut Ugur.

Anatolia did not explain the change of name.

Guler said investigators were still looking into indications the attacks were coordinated from abroad, and that there were strong hints the four bombings were connected.

But "in order to confirm this officially (we) have to discover all the proof," he said.

Police have now identified all of the bombers - two at Istanbul synagogues on November 15, leaving 27 people dead, and at the British consulate and HSBC building on November 20, claiming 30 lives.

Yusuf Polat, who is suspected of giving the order for the suicide attack on one of the synagogues was charged Saturday with attempting to violently overthrow the constitutional order, the most serious charge so far laid against any of those detained over the Istanbul attacks.

Anatolia said that searches in a residence used by Polat uncovered material used in making the kind of bomb detonated at the Beth Israel synagogue. – Sapa-AFP.