Iran fired on Israel following Israeli strikes in the Lebanese capital Beirut.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israeli strikes targeting military, government and infrastructure sites.
Following the announcement of a two-week ceasefire, initial U.S.-Iran talks in Pakistan in April failed to reach a peace deal.
Trump later announced the open-ended extension of the ceasefire and the continuation of a U.S. blockade until negotiations are concluded "one way or the other."
President Donald Trump said in a post to social media on Monday that Israel and Iran "are looking to do an immediate CEASEFIRE!"
"Final negotiations on 'Peace' are proceeding, subject to ignorance or stupidity getting in its way," Trump wrote, adding that the U.S. blockade of Iranian ports will remain until a deal is reached.
Sadegh Larijani, the head of Iran's Expediency Discernment Council and the brother of slain senior official Ali Larijani, said on Monday that Tehran's attacks on Israel "in defense of Lebanon" indicate "the formal declaration of a strategic doctrine."
Larijani said the Iranian attacks "sent a clear message that if one side of the Axis of Resistance is attacked, it will trigger a response that extends beyond geographical borders and will change the region's equations," as quoted by the semi-official Tasnim News Agency.
The Axis of Resistance refers to the Iranian-led grouping of militias spread around the Middle East through which Tehran has traditionally sought to build deterrence against and erode the influence of Israel, the U.S. and their regional partners. Lebanese Hezbollah is a key part of the axis.
President Donald Trump posted to social media on Monday morning demanding that Israel and Iran "immediately stop 'shooting.'"
The U.S. military recently shot down four Iranian drones that had been launched toward the Strait of Hormuz, U.S. Central Command said Friday.
"The attack drones posed an immediate threat to regional maritime traffic," CENTCOM said.
In response, CENTCOM said U.S. forces struck "Iranian coastal surveillance radar sites" in the city of Goruk and on Qeshm Island "to defend against further attacks."
This is the latest incident during the ceasefire where CENTCOM has said it defended against an Iranian action and then launched strikes at Iranian targets.
