BEIRUT: At least 37 people were killed and dozens wounded on Thursday in two suicide bomb blasts in a crowded district in Beirut's southern suburbs, a stronghold of the Hezbollah militant group, Lebanon's Interior Minister Nouhad Machnouk said.

The blasts occurred almost simultaneously and struck a Shia community centre and a nearby bakery in the commercial and residential area of Borj al-Barajneh, security sources said.

Machnouk said that the attackers were on foot and wearing explosive vests, adding that a third suicide bomber had been killed by one of the explosions.

There was no immediate claim of responsibility.

The blasts, which were also close to a closely guarded Hezbollah-run hospital, were the first attacks for more than a year in a stronghold of the insurgent group, which has sent fighters to Syria to fight alongside President Bashar al-Assad's forces in the country's civil war.

Medics rushed to treat the wounded after the explosions, which damaged shopfronts and left the street stained with blood and littered with broken glass, where security forces were trying to cordon off the scene and keep people from gathering.

Lebanon's Prime Minister Tammam Salam condemned the attacks as “unjustifiable”, and called for unity against “plans to create strife” in the country, urging officials to overcome their differences.

He announced a national day of mourning for Friday, local media reported.

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 blasts.

“When the second blast went off, I thought the world had ended,” he said.

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.

The army set up checkpoints at all entrances to the southern suburbs and Hezbollah's own security force was on high alert.

Several bomb blasts struck Lebanon in June last year, in a spillover of violence linked to Syria.

The war in Lebanon's larger neighbour, with which it shares a border of more than 300 km, has ignited sectarian strife in the multi-confessional country, leading to bombings and fighting between supporters of the opposing sides in Syria.

The bombers struck as Lebanese lawmakers held a legislative session for the first time in over a year. An ongoing political crisis has left the country without a president for 17 months, with the government failing to take even basic decisions.