Islamic State (IS) says it was behind the suicide bomb attacks that killed over 40 people and wounded dozens of others in a southern suburb of Beirut.

The attacks happened minutes apart at a Shia community centre and nearby bakery in the Borj al Barajneh area during the evening rush hour.

In a statement posted on Twitter, IS said its members detonated a bike loaded with explosives and when people gathered a suicide bomber blew himself up among them, killing 40.

Medics have put the death toll at 41, while the Lebanese Red Cross says a further 181 people people were injured in the blasts.

A Lebanese security official gave a different version of events to IS, saying the first attacker set off his explosives vest outside the community centre, while the second blew himself up inside the bakery.

An apparent third suicide bomber was found dead, his legs blown off, wearing an intact explosives' belt, the official added.

It is thought he may have been killed by the explosion at the bakery as his body was reportedly discovered nearby.

Al Mayadeen television also reported there was a third would-be attacker, describing him as a bearded young man.

Southern Beirut is a stronghold of Lebanon's militant Hezbollah group, which is fighting in Syria alongside president Bashar al Assad's forces.

The area has been targeted in the past by Sunni extremists over Hezbollah's involvement in Syria, but the latest attack is the first since June 2014.

Hezbollah has denounced it as a "crime" and vowed to continue its fight against "terrorists".

"What happened here is a crime... this battle against terrorists will continue and it is a long war between us," Hussein Khalil, an assistant to the group's leader, said at the scene.

Local hospitals have called on people to donate blood and appealed for residents not to gather at their gates so emergency staff can get in and out unhindered.

Ambulance crews arrived soon after the explosions and began taking away the wounded and the dead, as Lebanese troops and Hezbollah gunmen set up cordons.

Ambulance sirens could still be heard in the streets an hour later.

Hezbollah called on people to leave all the local coffee shops, which are usually packed with people, and urged residents to inform them of any suspicious activity.