VIDEO: Trump announces destruction of Iran's tallest bridge

US President Donald Trump said on Thursday the tallest bridge in Iran had been destroyed, hours after threatening to bomb the country "back to the Stone Ages."

Trump posted footage on social media of smoke rising from the B1 bridge in Karaj, around 35 kilometres southwest of Tehran - and warned that there would be further destruction unless Iran comes to the table to end the five-week war.

"The biggest bridge in Iran comes tumbling down, never to be used again - Much more to follow! IT IS TIME FOR IRAN TO MAKE A DEAL BEFORE IT IS TOO LATE, AND THERE IS NOTHING LEFT OF WHAT STILL COULD BECOME A GREAT COUNTRY!" Trump said.

Iranian state television had earlier reported two US-Israeli strikes on the bridge.

"A few minutes ago, the American-Zionist enemy once again targeted the B1 bridge in Karaj," state TV said, adding that an initial strike had caused two civilian casualties.

It said the later attack took place as emergency teams were deployed to the site to help victims of the first strike.

The B1 bridge, which was still under construction, is considered the Middle East's tallest according to Fars/Iranian media, with a 136-meter column.

Trump delivered a speech Wednesday in which he argued that the war launched by the United States and Israel on Feb.28 was almost over - even as he threatened to bomb Iran "extremely hard" if it didn't bow to his demands.

"Over the next two to three weeks, we are going to bring them back to the Stone Ages, where they belong," he said in his first prime-time address to the nation on the war.

Agence France-Presse