At least 37 people were killed and dozens wounded in two suicide bomb blasts in a crowded district in Beirut's southern suburbs, a stronghold of the Shi'ite Muslim militant movement Hezbollah.

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

Interior Minister Nouhad Machnouk said a third suicide bomber had been killed by one of the explosions.

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 Iran-backed Hezbollah, 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.

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