Tens of thousands of Iranians reportedly turned out Saturday in Tehran to view the coffin of Ayatollah Ali Khamenei, the Islamic Republic's leader for 37 years before being killed in February at the start of the U.S.-Israeli war on Iran.

Mourners dressed in black and were draped in the red, white and green flags of the Islamic Republic of Iran, according to Reuters.

The mass funeral is part of a roughly week-long memorial service that started late this week and will end early next week. 

Khamenei was killed in the first round of airstrikes, reportedly by Israel. Also killed in the strikes were Khamenei's daughter, grandchild, daughter-in-law and son-in-law, according to Iranian state media.

The funeral follows a day of Khamenei lying in state indoors for senior Iranian leaders and foreign officials to visit. China and India are among the countries sending representatives, according to CNN. 

Iran’s military and security institutions vowed revenge for Khamenei’s death, and chants of “Death to America” echoed through the Mosalla, state broadcaster Seda va Sima said, also according to Reuters.