The explosions, which appeared to be coordinated, went off outside two mosques as Friday prayers ended in the largely Sunni Muslim city.
“I see seven bodies inside several burned cars,” said a Reuters witness, speaking from near the Taqwa mosque, which is frequented by Sunni Islamist hardliners, where the first blast occurred.
A security source said several people were killed in the second blast outside Al-Salam mosque.
Ambulances rushed to the scene and heavy black smoke covered the sky. Television footage showed crushed cars with their windows smashed. Some cars were burning. People ran through the streets carrying a woman whose face was obscured by blood.
Two bodies could be seen on the ground and apartment blocks had their windows smashed.
“There are many casualties in the two mosques, we still do not have a clear idea of the figures,” a security source said.
The explosions came a week after a huge blast killed at least 24 people in a southern suburb of Beirut, a Shi’ite Hezbollah militant group stronghold.
Sectarian tension in Lebanon is being stoked by the conflict in neighboring Syria. Many of Lebanon’s Shi’ite Muslims support Syrian President Bashar Al-Assad, who is fighting a largely Sunni insurgency against his rule.