The state funeral for slain Iranian Supreme Leader Ali Khamenei began in Tehran, drawing crowds that The Guardian said could reach up to 30 million people across six days of ceremonies.

Khamenei was killed on February 28 in an airstrike, according to both NPR and The Guardian. NPR reported that the strike was the opening blow of a war launched by the United States and Israel. Khamenei had led Iran for 37 years, The Guardian said.

The Grand Mosalla mosque is serving as the central venue for the proceedings. The mosque sits in central Tehran, and The Guardian described it as sprawling. Thousands of mourners waited through the night to enter the grounds, the outlet reported, and by 5:30 a.m. the surrounding streets were already filling with crowds. The Guardian noted that some attendees had traveled for hours to reach the site.

Many mourners carried flags or posters of Khamenei, The Guardian said. Crowds chanted "Death to America and Israel," according to the same outlet. The Guardian also reported that the funeral events had been delayed before finally getting underway.

According to The Guardian, the proceedings are designed to convey Iran's sense of loss over Khamenei's killing, as well as a desire for revenge. Iran is staging mass processions as part of the multi-day observance, the outlet said. The funeral, which NPR confirmed opened in Tehran following the February 28 airstrike that ended Khamenei's more than three decades in power, is set to continue for nearly a week.