A source close to Hezbollah told AFP that an Israeli air strike on Friday killed the group's elite Radwan unit chief, while the Israeli military said it conducted "a targeted strike" on the Lebanese capital.
"The Israeli air strike killed Radwan Force commander Ibrahim Aqil, its armed force's second-in-command after Fuad Shukr," who an Israeli strike killed in July, also in Hezbollah's southern Beirut stronghold, said the source who requested anonymity to discuss sensitive matters.
Friday's strike was the third blamed on or claimed by Israel to hit the southern suburbs of Beirut since October when Hezbollah began cross-border clashes with Israel in support of Palestinian militants Hamas over the Gaza war.
The latest strike came days after deadly sabotage attacks on Hezbollah's communications devices sent tensions soaring.
"Israel conducted an air strike on the Beirut southern suburbs near Al-Qaem mosque," a Lebanese security source told AFP, requesting anonymity to discuss sensitive matters.
The Israeli military said it carried out a "targeted strike" in Beirut.
In a "preliminary toll," Lebanon's health ministry said the strike killed a total of three people, and hospitals received 17 wounded.
Hezbollah's Al-Manar television broadcast live footage from the scene of the attack that showed ambulances rushing to the area and transporting injured people on stretchers.
Lebanon's state-run National News Agency reported "an enemy raid targeting an apartment in a residential building in the Al-Jamous area of the southern suburb" of Beirut.
The previous strikes on south Beirut killed Shukr on July 30 and Hamas deputy leader Saleh al-Aruri on January 2.