Security officials say the explosions occurred minutes apart in an area called Burj al-Barajneh during rush hour on Thursday evening. The officials spoke on condition of anonymity in line with regulations.
George Kittaneh, head of the Lebanese Red Cross operations, told Lebanon's LBC television that three people were killed and "many others wounded."
Southern Beirut is a stronghold of Lebanon's militant Hezbollah group that it fighting in Syria along with government forces there.
The area has been hit in the past. Sunni militant groups have threatened to carry out more such attacks.