Iran has long said any peace deal with the US would depend on a ceasefire also holding in Lebanon, which Israel invaded in March in pursuit of Iran-aligned Hezbollah fighters who fired across the border.
There was no immediate formal response from Iran to Sunday's Israeli strikes on the southern outskirts of Beirut but influential Iranian MP Ebrahim Rezaei posted on X that Iran would deliver a "decisive and painful response".
"Look at the sky of the occupied territories tonight," wrote Rezaei, who serves as the spokesman for parliament's national security committee.
The US and Iran have shown little progress in reaching a deal to end the war that President Donald Trump launched in February with a campaign of air strikes alongside Israel against Iran.
Trump has repeatedly threatened to restart the strikes unless there is an agreement soon.
"We're very close to a deal, or I'm going to blow the hell out of them," Trump told NBC News in an interview, broadcast to mark 100 days of the conflict.
Trump has leaned on Israel to scale back its campaign in Lebanon to allow room for a peace deal with Iran, including rebuking Prime Minister Benjamin Netanyahu with obscenities in a phone call last week.
After the call, Netanyahu called off air strikes on Beirut and agreed the latest truce plan with the Lebanese government.
But Israel has never fully halted its campaign in Lebanon, which has killed thousands of people and driven hundreds of thousands from their homes.
Hezbollah, which was not party to the truce and would be dismantled under its terms, has also continued attacks and says it will not give up its weapons unless Israel halts fighting and withdraws.
Netanyahu said Sunday's strike on Beirut's southern outskirts, a district known as Dahiyeh that has long been a Hezbollah stronghold, was ordered in response to Hezbollah firing toward Israel.
The Israeli military had earlier said it had intercepted two projectiles fired over the border.
It issued an order for people to leave the southern Lebanese city of Tyre and surrounding areas ahead of possible strikes there.
Elsewere in Beirut on Sunday, mourners held a military funeral for Brigadier General Wissam Sabra, a senior military officer killed in a strike on his vehicle in the south the previous day.
The wider war has been stalemated since the United States and Israel paused their attacks on Iran in early April, with Iran blocking most shipping through the Strait of Hormuz, the main transit route for Middle East oil.
The US has imposed its own blockade of Iranian ports.
Although the sides have both said they are close to a preliminary agreement that would reopen the strait, they have repeatedly traded strikes, with escalations in recent days that have included attacks on nearby Arab countries hosting US bases.
US forces struck Iranian coastal radar sites in Goruk and Qeshm Island, both in the Strait of Hormuz, early on Saturday after shooting down drones launched by Iran that US Central Command said posed a threat to maritime traffic.
Two more Iranian attack drones that were threatening shipping in the strait were shot down, the US military said late on Saturday.
Iran's Revolutionary Guards said they retaliated against US bases in Kuwait and Bahrain.
Kuwait's army said it engaged seven ballistic missiles that passed over residential areas, resulting in material damage but no casualties.
