The bombing targeted a busload of Revolutionary Guards in the volatile southeastern province of Sistan-Baluchistan It came just days after Iran held more than a week of celebrations for the 40th anniversary of the Islamic revolution, which overthrew the US-backed shah TEHRAN: President Hassan Rouhani vowed revenge Thursday against the “mercenary group” behind a suicide bombing which killed 27 troops in southeastern Iran and accused the US and Israel of supporting “terrorism.” “We will certainly make this mercenary group pay for the blood of our martyrs,” the official IRNA news agency quoted the Iranian president as saying in response to Wednesday’s attack. Rouhani was speaking at Tehran’s Mehrabad Airport before leaving for the Russian resort of Sochi for a summit with his Russian and Turkish counterparts Vladimir Putin and Recep Tayyip Erdogan on the future of war-battered Syria. The bombing was claimed by Jaish Al-Adl (Army of Justice), which is blacklisted as a terrorist group by Iran, the SITE Intelligence Group reported. The organization was formed in 2012 as a successor to Sunni extremist group Jundallah (Soldiers of God), which waged a deadly insurgency for a decade before being severely weakened by the capture and execution of its leader Abdolmalek Rigi by Tehran in 2010. The European Union condemned the attack, saying “there can be no justification for such an outrageous act of terror,” and expressing condolences to the families of the victims. The bombing, which targeted a busload of Revolutionary Guards in the volatile southeastern province of Sistan-Baluchistan, was one of the deadliest attacks on Iranian security forces in years. It came just days after Iran held more than a week of celebrations for the 40th anniversary of the Islamic revolution, which overthrew the US-backed shah.