The strike appeared to be targeted at the Islamic Group's emergency and relief center in Hebbariyeh village in Southern Lebanon.
One of the tower's 300 residents told Reuters that Israel gave them a 30-minute warning to flee the building at night.
Stabbing attack carried out in West Bank, IDF soldier wounded • Gaza hostages' families protest outside the US consulate in Jerusalem
Syrian air defenses shot down a number of missiles, state media said, without giving details on the targets hit.
In a second statement sent following Washington's criticism, the military said an examination of its operational systems ruled out that its forces had struck the center.
Wissam al-Tawil is the most senior member of Hezbollah to be killed in an Israeli strike.
Three security sources and Iranian state media said an Israeli air strike outside Damascus on Monday killed Sayyed Razi Mousavi.
Hamas has a history of reporting that hostages were killed in airstrikes after they had been executed by the terrorist group.
The couple's wedding was scheduled to take place on Tuesday night, at a hall in their hometown of Ofakim, near the Gaza border.
Syria is an important player today because it intersects with major tectonic changes in the region, changes that relate to diplomatic developments.