State media said the bridge, located near Karaj west of Tehran, was hit while people were under the structure and along the riverbank. Witness videos shared online showed smoke rising around the bridge and several explosions as people ran for cover.

The attack matters because it appears to have struck a civilian infrastructure site during a public holiday, adding to concern over the widening human cost of the war. Iranian officials said the B1 bridge was still under construction and due to open soon, with no military activity reported nearby. Foreign Minister Abbas Araghchi condemned the strike, saying attacks on civilian infrastructure reflected “moral collapse”.

US President Donald Trump later posted footage claiming to show the collapse of Iran’s “biggest bridge” and warned that there was “much more to follow”. Iranian media describe the 136‑metre structure as one of the tallest bridges in the Middle East. Independent verification of the exact footage and the full casualty toll remains difficult because of wartime reporting restrictions.