Slain Hezbollah leader Hassan Nasrallah's son-in-law, Hassan Jafar Qassir, was killed in an Israeli raid which targeted an apartment in a residential building in the Mezzeh district of Damascus, according to the Syrian Observatory for Human Rights.
Hassan is the brother of Muhammad Jafar Qassir, who was killed in an Israeli strike in Beirut two days ago. According to the Observatory, Muhammad was responsible for the transfer of Hezbollah weapons from Syria to Lebanon.
On Wednesday, media reports said Hassan Jafar Qassir was killed in an Israeli strike that hit the first floor of a three-story building frequented by Hezbollah and Iranian Revolutionary Guard Corps leaders in the Mezzeh district.
Three people were killed in the strike, including two non-Syrians. At least four unidentified people were injured.
The Mezzeh district is home to Syrian security and military headquarters, as well as embassies and UN agencies.
The targeted building is located about half a kilometer from the site of a raid that targeted last Tuesday two mini-buses, killing three civilians including a media worker, as well as three pro-Iran fighters, including a Hezbollah member, AFP reported.
Since Syria's civil war erupted in 2011, Israel has conducted hundreds of strikes in the country, targeting army positions and Iran-allied fighters, including Hezbollah.
The strikes have increased in recent days, including on areas near the border with Lebanon.
Tens of thousands of people have crossed into Syria over the past week, fleeing heavy Israeli airstrikes on Lebanon.
Israeli authorities rarely comment on individual strikes in Syria, but have repeatedly said they will not allow arch-enemy Iran to expand its presence there.