Bulgarian prosecutors have filed an indictment charging two Lebanese nationals with terrorism for their alleged involvement in a 2012 bombing in a Black Sea resort that killed five Israeli tourists and a bus driver, and left 35 Israelis injured.

"The indictment has been filed with a specialized criminal court," Chief Prosecutor Sotir Tsatsarov told reporters on Monday.

Meliad Farah, 35, a Lebanese national who holds an Australian passport, and Hassan El Hajj Hassan, 28, a Lebanese national who holds a Canadian passport, will face trial in absentia as their whereabouts are unknown.

Attempts by Bulgarian investigators to locate them using international legal assistance mechanisms have failed, but according to the chief prosecutor the trial will end with a verdict regardless of whether the suspects are handed over to Bulgaria or not.

On July 18, 2012, a 24-year-old Lebanese-born man with dual French-Lebanese citizenship, Mohamad Hassan El-Husseini, blew himself up on a passenger bus full of tourists at the airport in Burgas.

The two men charged in the indictment are alleged to have provided the explosive device and logistical support to the bomber, who died on the spot.

Earlier investigation into the terrorist attack established that it was the work of the military wing of Hezbollah. This led to the subsequent European Union decision to declare Hezbollah's military wing a terrorist organization.