Huge crowds of mourners poured into the streets of two Iranian cities on Sunday to pay their respects to Maj. Gen. Qassim Suleimani, the second most powerful figure in the country and leader of the elite Quds force, who was killed on Friday in an American drone strike near the Baghdad airport.

General Suleimani’s body was returned to Iran early Sunday — after tens of thousands of people joined processions for him in four Iraqi cities — and was received with military salutes at the airport in Ahvaz, a city in the southwest. A funeral procession then made its way through Ahvaz, the coffin draped in flowers and an Iranian flag, and depicting mourning symbols of the Shiite faith.

A mass of people snaked across the city’s main streets and a long bridge over the Karoun River. Stretching over 30 kilometers, or almost 20 miles, the crowds of men and women in black carried flags and photos of Mr. Suleimani and beat their chests in unison as Islamic prayers blasted from speakers around the city.

Iranian state television estimated that the mourners in Ahvaz and Mashhad, where the general’s body was flown later for another procession, numbered in the millions.