A Lebanese group linked to al-Qaeda has claimed responsibility for Tuesday's double suicide bombing outside Iran's embassy in Beirut that killed at least 23 people, including a senior Iranian diplomat, and wounded more than 100 others.
The bombing in the Lebanese capital was one of the deadliest in a series of attacks targeting Hezbollah, the Shia armed group, and Shia strongholds in the country in recent months.
The Abdullah Azzam Brigades has said the attack is a "message of blood and death" to Iran and Hezbollah - both supporters of Syrian President Bashar Assad.
Iranian embassy sources told Al Jazeera that five security guards besides the diplomat were among the dead.
The diplomat was identified by Ghazanfar Roknabadi, the Iranian ambassador, as Ibrahim Ansari, who took up his post a month ago and was overseeing regional cultural activities.
Also among the dead was Radwan Fares, a Lebanese national who headed the facility's security, according to a Lebanese official at the Iranian embassy.
Ban Ki-moon, the UN secretary-general, speaking through the organisation's deputy spokesman Farhan Haq, condemned the attacks and called on all Lebanese to recognise that "such appalling and indiscriminate acts of violence" target everyone in the country.
John Kerry, US secretary of state, called the bombings "senseless and despicable", and said "our hearts go out to the Iranian people after this violent and unjustifiable attack claimed the life of at least one of their diplomats".
The midmorning explosions hit Janah, a Hezbollah-dominated neighbourhood and home to several embassies and upscale apartments, leaving bodies and pools of blood on the glass-strewn street amid burning cars.
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The first suicide attacker was on a motorcycle with 2kg of explosives and blew himself up at the Iranian embassy's black main gate, damaging the three-storey facility, a Lebanese security official said.
Less than two minutes later, a second suicide attacker driving a car rigged with 50kg of explosives struck about 10 metres away, the official said.
In the chaotic aftermath, volunteers tried to extinguish bodies still aflame from the blast by covering them with their sweaters and blankets.
"The sheer scale of the destruction is an indication as to how powerful the explosives were," Al Jazeera's Zeina Khodr, reporting from near the site on Tuesday, said.
The official Iranian news agency, IRNA, quoted a Foreign Ministry spokesman as saying the bombings were "an inhuman crime and spiteful act done by Zionists and their mercenaries". Israel denied any links.
Syria's government said the attacks "reek of petrodollars" - a reference to oil-rich Gulf Arab countries such as Saudi Arabia and Qatar that back the rebellion against Damascus.
The Abdullah Azzam Brigades, which has previously fired rockets at Israel from Lebanese territory, claimed responsibility for the Beirut attack in a Twitter post.
"This is a double-martyrdom operation carried out by two heroes from the heroic Sunnis of Lebanon," Sirajeddin Zreikat, a member of the group, said.
"Operations will continue in Lebanon until two demands are met: first, withdrawing Hezbollah members from Syria; second, release our prisoners from jails of injustice in Lebanon."
Ali Mikdad, a Hezbollah politician, told the local Lebanese staion, Al-Mayadeen TV: "We tell those who carried out the attack, you will not be able to break us. We got the message and we know who sent it and we know how to retaliate."
The bombing is expected to pull Lebanon further into a conflict that has torn apart the deeply divided country, and came as Assad's troops, aided by Hezbollah fighters, captured a key town near the Lebanese border from rebels.
The Syrian army's border offensive is part of a larger government push that started last month and has seen forces loyal to Assad firmly seizing the momentum in the war, taking one rebel stronghold after another.
Source: Al Jazeera and agencies