Turkish prosecutors have already asked for some of the suspected accomplices in the blast.
Bulgarian prosecutors have charged five people for supporting terrorist acts in connection with an explosion in central Istanbul that killed six people on Nov. 13, the country's chief prosecutor Ivan Geshev said on Saturday.
Three men of Moldovan origin and a man and woman of Syrian Kurdish descent were detained by Bulgarian special police forces earlier this week following investigations and close cooperation with prosecutors in neighbouring Turkey, Geshev told Reuters.
"Five people have been charged. The charges are in two groups - for supporting terrorist acts in another country, namely the attack in Istanbul, and for human trafficking," Geshev said.
"These people were mainly involved in human trafficking through the border (with Turkey) and smuggling," he said.
Prosecutors will ask a Bulgarian court later on Saturday to keep the four men in detention, while a different option will be sought for the woman in light of a health condition, he said.
Turkish prosecutors have already asked for some of the suspected accomplices in the blast to be extradited, Geshev added.
On Friday, a Turkish court ordered the pre-trial detention of 17 people suspected of being involved in the explosion, including the suspected bomber, who police identified as Syrian national Ahlam Albashir.
No group has claimed responsibility for the blast, which also injured more than 80 people on Istiklal Avenue, a busy and historic pedestrian strip.
The Turkish government swiftly blamed Kurdish militants for the blast and police have said the suspected bomber was trained by Kurdish militants in Syria.
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