Videos show ambulances on the scene and the attack appears to have targeted an apartment.
A Lebanese security source tells AFP that two people have been killed with ties to al-Jamaa al-Islamiyya, a Sunni movement with close ties to Hamas. According to the source, it was an Israeli drone attack.
It would be the first time Israel has carried out an attack so centrally in Beirut since the latest round of hostilities broke out. Israel has not commented on the incident.
Over the past week, Israel has primarily targeted Beirut's southern suburbs, where Hezbollah leader Hassan Nasrallah was killed on Friday.
On Sunday, more than 100 people were killed in Israeli attacks, according to Lebanon's Health Department.
Israel continued its attacks on areas in the Bekaa Valley east of Beirut overnight Monday, according to the Israeli military (IDF). A dozen launch pads and weapons depots were attacked, according to a statement. The attacks on Hezbollah also continued in southern Lebanon overnight, according to IDF.
The war is also raging on in Gaza. Israel's military reported just after midnight that a school building in northern Gaza had been attacked. According to IDF, Hamas had a military command center in the building.
