"Luckily the school was closed because of the Covid-19 pandemic," local official Mohammad-Bagher Honarvar told state television.

The aircraft was on a training mission when it went down around 9:00 am (0530 GMT) in the city's central district of Monajem, said Honavar, who heads a crisis management unit in East Azerbaijan province.

The head of the local Red Crescent organisation said the plane crashed into an external wall, and that one of the dead was a nearby resident.

A blaze broke out at the crash site and firefighters were seen battling the flames as a crowd looked on, in video footage by the official news agency IRNA.

The charred remains of the warplane could be seen amid the rubble of the school's blackened facade.

The plane had been stationed at the Shahid Fakouri air base in Tabriz, base commander General Reza Youssefi told the broadcaster, adding that it was heading back from the training mission when it encountered a technical problem that prevented it from landing.

- Ageing fleet -

Iran's airforce has some 300 warplanes, mostly Russian MiG-29 and Sukhoi-25 fighters that date back to the Soviet era, as well as Chinese F-7s, and French Mirage F1s.

The fleet also includes some American F-4 and F-5 jets that date back to the regime of the Western-backed shah, who was ousted in the 1979 Islamic revolution.

Experts say that only some of these aircraft are operational.

In August 2006, Iran announced it had developed a new warplane named "Azarakhsh" (Lightning) which it described as similar to the F-5.

A year later it unveiled another home-grown jet calling it "Saegheh" (Thunder), saying it was similar to the American F-18.

But some Western military experts have said the Saegheh is a derivative of the F-5.

Monday's fighter jet crash was the first accident involving a military plane reported by Iran since December 2019.

Back then, a MiG-29 warplane went down near a dormant volcano in the country's northwest during a test flight, according to official media.

Three days later the military confirmed the death of the pilot.

In January 2019, a military cargo plane overshot a runway, crashed and caught fire during a botched landing near the capital Tehran.

At the time the army said 15 people were killed in the accident.

A combat jet also crashed in Tabriz during military exercises in September 2011, local media reported.

Iran has been subject to severe US sanctions since 2018 when the US withdrew from a landmark nuclear deal struck three years earlier between Tehran and world powers.

Talks are underway in Vienna to revive the deal and Iran is calling for sanctions to be lifted.