BEIRUT (AFP) - The Islamic State in Iraq and Syria (ISIS) group claimed a twin bomb blast that killed 41 people in a Beirut stronghold of the Shi'ite Hezbollah movement Thursday, in a statement posted online.

"Soldiers of the Caliphate" detonated explosives planted on a motorbike in an area frequented by Shi'ites, using a derogatory term to refer to the sect, the statement said.

"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.

The claim could not be independently verified but the statement followed the usual format of ISIS claims of responsibility and was circulated on extremist online accounts.

The army said the attacks had been carried out by two suicide bombers and that the body of a third bomber who had failed to detonate his explosive device had been found at the scene of the second blast.

The attack hit a busy shopping street in a neighbourhood in the southern suburbs of Beirut where Hezbollah holds sway.

It comes after a string of attacks in 2013 and 2014 targeting the groups by Sunni extremist groups who cited Hezbollah's military support for Syrian President Bashar al-Assad.