Iranians gather at Valiasr Square in central Tehran to mourn the death of President Ebrahim Raisi.  [Atta Kenare, AFP]

Thousands of Iranians walked sombrely through the streets on Tuesday for the funeral procession of President Ebrahim Raisi and seven members of his entourage who were killed in a helicopter crash.

Waving Iranian flags and portraits of the late president, the mourners set off from a central square in the northwestern city of Tabriz, where Raisi was headed when his helicopter crashed on Sunday.

They walked behind a lorry carrying the coffins of Raisi and his seven aides.

The helicopter lost communication while it was on its way back to Tabriz after Raisi attended a joint inauguration of a dam with his Azeri counterpart, Ilham Aliyev, on their common border.