An Israeli air strike targeted a senior Hezbollah commander in Beirut's southern suburbs late on Tuesday.
The Israeli military said it was in retaliation for a cross-border rocket attack three days before that killed 12 children and teenagers.
A loud blast was heard and a plume of smoke could be seen rising above the southern suburbs - a stronghold of the armed group Hezbollah - at around 7:40 pm (1640 GMT), a Reuters witness said.
A senior Lebanese security source said a senior Hezbollah commander had been the target of the air strike and his fate remained unclear.
Lebanon's state-run national news agency said an Israeli air strike had targeted the area around Hezbollah's Shura Council in the Haret Hreik neighbourhood of the capital.
Beirut has been on edge for days ahead of an anticipated Israeli attack in reprisal for the rocket strike on the Israeli-occupied Golan Heights on Saturday that killed the 12 youngsters in a football field in a Druze village.
Hezbollah has denied involvement in that attack.
As diplomats sought to contain the fallout, US Defence Secretary Lloyd Austin said he did not believe a fight was inevitable between Hezbollah and Israel, though he remained concerned about the potential for escalation.
The US Justice Department released thousands of heavily redacted documents related to the late financier and convicted offender Jeffrey Epstein on Friday that extensively featured Democratic former President Bill Clinton.
The US military launched large-scale strikes against dozens of IS targets in Syria on Friday in retaliation for an attack on American personnel, US officials said.
A Pakistani court on Saturday sentenced former Prime Minister Imran Khan and his wife Bushra Bibi to 17 years in prison each in a corruption case involving the under-priced purchase of luxury state gifts, the court and Khan's lawyers said.
Seven elephants were killed and one injured when a Delhi-bound train collided with a herd in northeast India early on Saturday, district police chief VV Rakesh Reddy said.
Five Palestinians were killed in an Israeli attack on a school sheltering displaced people in the Al-Tuffah neighbourhood, east of Gaza City, the head of Al Shifa Hospital in Gaza City, Mohamed Abu Selmia, told Reuters on Friday.