Iran's ambassador to Bulgaria reiterated Friday that Tehran was in no way involved in a bomb attack that killed five Israelis in July, after Sofia blamed Hezbollah.
"The Burgas attack has nothing to do with Iran," Gholamreza Bagheri told reporters, adding that his country "condemned terrorism in all its forms."
Earlier this week the Bulgarian government said that two Australian and Canadian passport-holders with links to Hezbollah's military wing were behind the deadly blast at Burgas airport.
The explosion on the bus carrying Israeli tourists also killed the vehicle's Muslim Bulgarian driver as well as the still-unidentified bomber.
Immediately after the attack, the deadliest on Israelis abroad since 2004, Israel blamed Iran and its "terrorist proxy" Hezbollah. Iran has always denied involvement.
Hezbollah, whose political arm is the most powerful faction in the current Lebanese cabinet, this week hit out at Israel for waging "an international campaign" against it.
Bulgaria's announcement led to renewed calls from Washington and Israel on the 27-nation European Union to designate the Lebanese Shiite movement a "terrorist" organisation.
Diplomats in Brussels told AFP that Britain and other EU members are in favour but that with key countries like France and Italy reluctant, there is little prospect of achieving the consensus required.