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 UN Secretary General António Guterres has warned prospects for peace between Israelis and Palestinians are increasingly fragile, urging urgent international action to prevent the collapse of a two-state solution.
Pakistan's security forces used drones and helicopters to wrest control of a southwestern town from separatist insurgents after a three-day battle, police said on Wednesday, as the death toll in the weekend's violence rose to 58.
The most prominent son of late Libyan leader Muammar Gaddafi, Saif al-Islam Gaddafi, has been killed, sources close to the family, his lawyer Khaled el-Zaydi and Libyan media said on Tuesday.
The Sudanese army said it broke a years-long siege on the city of Kadugli on Tuesday, potentially providing tens of thousands of people a reprieve from famine and signalling a shift in the war's momentum.
A World Health Organisation (WHO) official said on Tuesday that the first five patients were transferred through Gaza's Rafah crossing with Egypt, which reopened on Monday.