Three people belonging to a Palestinian organisation were killed in an Israeli strike on the heart of Beirut on Monday, the group said.
The strike was the first Israeli attack on Beirut within the city's limits since the outbreak of the war in Gaza last year.
The Popular Front for the Liberation of Palestine (PFLP), a secular left-wing group, has aligned with Hezbollah in its support of the Palestinian group Hamas against Israel.
The PFLP said in a statement that its military security chief Mohammad Abdel-Aal, military commander Imad Odeh, and Abdelrahman Abdel-Aal were killed in the strike on Beirut's Kola district.
A Lebanese security source said four people were killed in the strike that had targeted an apartment belonging to members of the Lebanese Islamist group Jamaa Islamiya.
Television footage showed the partially flattened floor of the building targeted by the strike, in the predominantly Sunni neighbourhood of Kola, near the road linking the capital to Beirut airport.
AFP journalists reported drones flying over the Lebanese capital throughout Sunday.
The Israeli army has also shelled the southern suburbs of Beirut, Hezbollah's stronghold, on several occasions in recent days.
Formed in 1960, Jamaa Islamiya, like Hamas, traces its origins to the Muslim Brotherhood. It has been the target of several Israeli strikes since the escalation began on the Israeli-Lebanese border.
Strikes on Hezbollah strongholds across Lebanon killed at least 105 people on Sunday, two days after an Israeli strike killed the group's longtime leader Hassan Nasrallah.
Hezbollah launched low-intensity cross-border strikes on Israeli troops after its Palestinian ally Hamas staged its unprecedented attack on Israel on October 7, sparking the war in the Gaza Strip.
Nearly a year later, Israel announced a shift in its focus to battling Hezbollah on its northern front.
