One of Hezbollah's commanders was killed in Beirut, the militant group said.
This is the house of Hassan Al-Laqqis, where the assassination took place around midnight.
The commander was shot in the head while he was driving his car. A gun with a silencer was used.
Hezbollah is blaming Israel, an old rival with whom it fought a month-long war in 2006.
The group describes Al-Laqqis as a leader of the Islamic resistance against the Jewish state.
Israel denied any role in the killing.
A source has said Al-Laqqis had joined battles in neighbouring Syria.
The Shi-ite group has been sending fighters to Syria to support President Bashar al-Assad against mostly Sunni rebels. Such intervention has fueled sectarian violence in Lebanon.
