Tehran accused Israel of carrying out deadly double blasts on Tuesday outside the Islamic republic's embassy in Beirut that killed two Iranians, including a diplomat, according to media reports.
The bombings were "an inhuman crime and spiteful act done by Zionists and their mercenaries," foreign ministry spokeswoman Marzieh Afkham said in remarks carried by the official IRNA news agency.
Israel is Iran's main regional arch-foe whose existence Tehran does not recognise. The two do not see eye to eye over a number of issues, including Iran's disputed nuclear drive.
Afkham also confirmed that Iran's cultural attache Ibrahim Ansari, a mid-ranking Shiite cleric, was killed in the bombings.
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In Tehran, state television and the Mehr and Fars news agencies said the second Iranian killed in the blasts was a security guard who had been manning the embassy's gate.
The powerful explosions just opposite the multi-storey embassy in the southern suburbs of the Lebanese capital killed at least 23 people, wounded almost 150 others and caused widespread damage.
They follow two other bomb attacks this year in the southern suburbs of Beirut that are the bastion of the powerful Lebanese Shiite movement Hezbollah.
The group, which is sponsored by Iran, has drawn controversy for sending thousands of fighters into neighbouring Syria to support the regime of President Bashar al-Assad as he battles a 32-month-old uprising.