U.N. Security Council chief Ban Ki-moon condemned the attacks, while EU foreign policy chief Catherine Ashton said she “appalled by the bombing.”
Lebanese leaders called for national unity.
President Michel Suleiman called his Iranian counterpart Hassan Rowhani and Ambassador to Beirut Ghazanfar Ruknabadi to denounce the attack, which resulted in the death of at least 23 people, including the Iranian cultural attaché.
The blasts occurred in an area considered a stronghold of the Lebanese Shiite movement Hezbollah, which is a main ally of Syrian President Assad in the civil war next door. It is not clear if the blasts are related to the Syrian civil war.
Suleiman called for national unity and urged the Lebanese to remain vigilant in the face of security threats present in the country as a result of the conflict next door, according to a statement carried by local Lebanese media.
“Such criminal messages do not alter convictions but merely yield the deaths of innocent people,” said Suleiman, who was in Kuwait to attend an Arab-African summit.
“The hand of terror will not be able to turn back the clock and reopen a black page in Lebanon’s history,” the president added.
In the statement, Suleiman also urged security officials to make to identify the perpetrators of the attack and bring them to justice.
Lebanon-based al Qaeda-linked group, the Abdullah Azzam Brigades, claimed responsibility and threatened further attacks unless Iran withdraws forces from Syria, where they have backed President Bashar al-Assad’s war against opposition fighters.
In a Twitter post, Sheikh Sirajeddine Zuraiqat, the religious guide of the Abdullah Azzam Brigades, said the group had carried out the attack. “It was a double martyrdom operation by two of the Sunni heroes of Lebanon,” he wrote.
Iran’s foreign ministry, meanwhile, accused Israel of carrying out deadly double blasts.
The bombings were “an inhuman crime and spiteful act done by Zionists and their mercenaries,” ministry spokeswoman Marzieh Afkham said in remarks carried by the official IRNA news agency.
U.S. Secretary of State John Kerry condemned the attacks as “senseless and despicable.”
“The United States knows too well the cost of terrorism directed at our own diplomats around the world, and our hearts go out to the Iranian people after this violent and unjustifiable attack,” Kerry said in a statement.
Iran and Assad’s ally Russia condemned the “bloody attack” targeting a “diplomatic mission” and called for punishing those responsible for fomenting violence in the volatile region, the Russian foreign ministry said in a statement.
“The incident again underscores the need to stop those who via a series of bloody attacks in Lebanon, in Syria, in Iraq and other countries in the Middle East and north Africa, seek to rekindle hatred between faiths, which is disastrous for the region and its people,” the statement said.