Interpol asked for help Thursday in identifying the alleged accomplice of a suicide bomber who killed six people in Bulgaria last month and distributed images of the suspect.
In a statement, the Lyon-based global policing body urged national police forces to distribute the images, released earlier this month by Bulgarian police.
Two computer-generated pictures shows a bulky-faced man with a dark complexion, black hair and brown eyes, in one case with glasses.
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Bulgaria's interior ministry has said it has "evidence that the man is linked to the terrorist act at Burgas airport".
An accomplice theory has been gaining ground since shortly after the July 18 attack, whose perpetrator has also remained unidentified.
Investigators have already released a computer-generated portrait of the presumed suicide bomber, based on pictures and data from coroners who examined his severed head found on the site of the attack.
The portrait showed a young man in his late 20s or early 30s with fair skin, light-coloured eyes, a high forehead and shortish dark brown hair.
The image was also circulated by Interpol and investigators have been trying to match DNA samples and fingerprints taken from the bomber's scattered remains with anything in international databases.
Israel has blamed Iran and its Lebanese ally Hezbollah for the attack, which killed five Israelis and their Bulgarian bus driver and injured more than 30 other tourists. Tehran has denied any involvement.