Thousands of people gathered Monday morning in the south-western Iranian city of Ahvaz for the funeral of those killed during an attack on a military parade.
AFP reporters saw members of the public and the military carrying coffins draped in the Iranian flag, some bearing pictures of the deceased.
Four militants attacked a Saturday parade marking the start of the 1980-1988 Iran-Iraq war, spraying the crowd with gunfire and killing 24 people.
State TV reported that 12 of the 24 dead would be buried in Ahvaz, about 560 kilometres (350 miles) south of Tehran, while the others will be buried in their home towns.
Mourners carried pictures of the dead along with banners reading “we will stand to the end” and “no to terrorism”.
Some waved the flags of Arab tribes from the region as sign of solidarity with the victims.
The ceremony in front of the Sarallah Mosque was attended by thousands of people including soldiers, clerics and officials.
Speakers included the wartime commander of the Islamic Revolutionary Guards Corps (IRGC), Lieutenant General Mohsen Rezai, deputy IRGC chief Brigadier General Hossein Salami and Intelligence Minister Mahmood Alavi.
Iranian authorities have blamed an Arab separatist group and accused the United States, Israel and Gulf Arab monarchies of backing Saturday’s “terrorist” attack.
The Islamic State group also claimed responsibility.