Twin blasts claimed by IS kill 41 in Beirut

More than 200 peple were wounded, many of them seriously, said Health Minister Wael Abou Faour at the scene of the explosions, in a narrow shopping street in the Burj al-Barajneh neighbourhood.

The attacks appeared to mark a return to the campaign against Hezbollah strongholds between 2013 and 2014, ostensibly in revenge for the militants' support of regime forces in neighbouring Syria's civil war.

Two men wearing suicide vests carried out the attack, said the army, while the body of a third who had failed to detonate his explosive device was found at the scene of the second blast.

The street in the poor mainly Shiite Muslim neighbourhood, normally home to a market, was stained red with blood according to an AFP photographer, who saw bodies inside nearby shops.

Surrounding buildings were badly damaged by the blasts and security forces were trying to cordon off the scene and keep people from gathering.

Sunni jihadist group IS claimed the attack, saying its "soldiers of the Caliphate" detonated explosives planted on a motorbike on the street, in an online statement.

"After the apostates gathered in the area, one of the knights of martyrdom detonated his explosive belt in the midst of them," the statement added, without referring to Hezbollah's involvement in Syria, much of which is under IS control.

The statement could not be independently verified, but it followed the usual format of IS claims of responsibility and was circulated on jihadist online accounts.

- 'The world had ended' -

Local television stations showed footage of wounded people being carried away by emergency services and civilians.

"I'd just arrived at the shops when the blast went off. I carried four bodies with my own hands, three women and a man, a friend of mine," a man who gave his name as Zein al-Abideen Khaddam told local television.

Another described the sound of the explosions: "When the second blast went off, I thought the world had ended."

The wounded were evacuated to several hospitals in the area, including the Bahman hospital in neighbouring Haret Hreik.

"We've received dozens of wounded people and they're continuing to arrive," a doctor there told AFP.

Lebanese Prime Minister Tammam Salam announced a national day of mourning for Friday, local media reported.

Former premier Saad Hariri, who leads a political bloc opposed to Hezbollah and its allies, called the attack "vile and unjustified". 

World leaders also condemned the attack, which French President Francois Hollande called "despicable".

The White House offered its condolences for what it described as the "horrific terrorist attacks", vowing that "such acts of terror only reinforce our commitment to support the institutions of the Lebanese state".

Un Secretary General Ban Ki-moon called on Lebanon to "not allow this despicable act to destroy the relative calm that has prevailed in the country over the past year".

- Campaign against Hezbollah -

The attacks were the deadliest to hit a Hezbollah stronghold since the group entered Syria's civil war in support of President Bashar al-Assad. 

Between July 2013 and February 2014, there were nine attacks on Hezbollah throughout Lebanon, mostly claimed by Sunni extremist groups.

In the most recent, in the southern suburbs of Beirut in June last year, a suicide car bomb killed a security officer.

Despite ostensibly targeting Hezbollah, the victims of the attacks have been overwhelmingly civilians.

The deadliest in southern Beirut was in 2013, when 27 people were killed by a car bomb in the Rweiss district.

The attacks were claimed by several different Sunni groups, but all cited Hezbollah's role in the conflict in Syria.

Hezbollah is a staunch ally of the Syrian regime and is backed by Iran, another key supporter of the Damascus government.

In early 2013, it dispatched fighters to back government forces against a Sunni-dominated uprising that began with anti-regime demonstrations in March 2011.

Since then, it has become deeply involved in the conflict, deploying fighters throughout the country to bolster Assad's troops on a range of battlefields.

At least 971 Hezbollah fighters have been killed in Syria, according to the Britain-based Syrian Observatory for Human Rights monitor.