Bulgaria has asked Australia, Canada, Israel and Lebanon for help investigating last year's bus bombing that killed six people, officials from its interior ministry said.
"The investigation is entering a new stage: collect direct evidence on the perpetrators of the attack," a top ministry official, Kalin Gueorguiev, said Saturday.
"Requests regarding the criminal investigation have been sent to several countries including Canada, Australia and Israel," he told private Nova television.
Interior Minister Tsvetan Tsvetanov said on Friday that a request had also been sent to Lebanon, where the bomber's two suspected accomplices live.
He spoke a day after revealing that the bomber who killed five Israeli tourists and their Bulgarian bus driver at Burgas Airport on Bulgaria's Black Sea coast last July had not intended to die.
The man "was not a kamikaze but only meant to put the ... explosive device in the baggage compartment of the bus and detonate it later from afar," he told reporters.
Tsvetanov said the two suspected accomplices had been identified as Australian and Canadian passport holders who "belonged to the military wing of Hezbollah".
Citing sources close to the case, the Standart daily reported Saturday that Bulgaria had asked Lebanon to arrest and interrogate the identified suspects.
It added that Sofia had asked Australia to confirm the identity of one of the suspects who had lived in Bulgaria under the false name of Brian Jameson and allegedly received a wire transfer from the Lebanese Shiite movement Hezbollah.
Canada has already confirmed the identity of the other suspect who went by the false name of "Ricco" in Bulgaria and had lived in Vancouver from age eight to 12.
The bomber's name is still not known, with his DNA and fingerprints failing to find matches in international databases. Investigators also believe a fourth person was involved.
Israel had immediately blamed Iran and its "terrorist proxy" Hezbollah for the attack.
Iran has denied any involvement, while Hezbollah denounced Israel for waging an "international campaign" against it, without specifically addressing the bombing.