Israel struck Beirut on Sunday in what it said was a response to Hezbollah rocket fire, on the day a US-Iran deal could be signed.
In a joint statement, Prime Minister Benjamin Netanyahu and Defence Minister Israel Katz said the Israeli military attacked Hezbollah sites in the Dahieh district of Lebanon's capital.
"Israel will not tolerate firing into its territory," they said. The military said the attack was a "precise strike" on a Hezbollah command centre.
US President Donald Trump said the attack "should not have happened, particularly on a special day" when the US is close to a deal with Iran. "This could be the beginning of a long and beautiful peace - let’s not blow it," Mr Trump wrote on social media.
Lebanese state media reported that at least three people were killed and 15 others wounded in the Israeli strike, which hit the Ghobeiry area of Beirut's southern suburbs.
Lebanon's National News Agency said that search and rescue operations were continuing at the site of the attack, with casualty figures remaining preliminary.
The strike also caused significant damage to neighbouring buildings and shops, according to the report.
The Israeli military said earlier on Sunday that Hezbollah launched three projectiles towards northern Israeli communities in what it described as a breach of the ceasefire between the sides. There was no immediate comment from the Iran-backed group on the Israeli claim.
The projectiles fell near the communities of Shomera and Shlomi, the military added. It said two other projectiles had crossed into Israeli territory at the weekend.
Israel and Hezbollah regularly exchange fire in southern Lebanon but the capital, including districts seen as bastions of the Iran-backed group, has been relatively spared of late, having been struck only twice since mid-April.
Israel's military struck Beirut's southern suburbs last Sunday, hitting apartments in two buildings. That led to one of the war's biggest flare-ups in weeks, as Iran launched attacks on Israel in protest against the war in Lebanon.
The regional crisis had cooled since then, with the US and Iran appearing close to agreed on an initial peace deal. US and Pakistani leaders had said the agreement could be signed on Sunday.
Iran has long made a halt to fighting in Lebanon a condition for any wider agreement with the US.
Also on Sunday, the Israeli military issued displacement orders for people in more than two dozen villages in southern Lebanon, saying it was set to act against Hezbollah targets in the area.
Earlier this month, US President Donald Trump said Hezbollah and Israel had agreed to stop attacking each other after weeks of intense fighting and fears Israel would increase attacks on Beirut. Mr Trump said he secured a pledge from Hezbollah to refrain from attacks on Israel and that Mr Netanyahu said his forces would not push deeper into Lebanon.
Almost 3,700 people have been killed in Lebanon by Israeli attacks since March 2. Of that toll, 730 were women, children or medics, Lebanon's Health Ministry said. Authorities have said about 1.2 million people have been displaced in Lebanon.
Hezbollah entered the war on March 2, saying it was retaliating for the killing of Iran's supreme leader Ayatollah Ali Khamenei at the start of the conflict.
Since then, 28 Israeli soldiers have been killed in combat in Lebanon, according to a Reuters tally of Israeli military announcements, while four civilians have been killed in Hezbollah attacks.
