Watch: 'Death to America, Israel' chants echo as Ayatollah Ali Khamenei's funeral begins

"Death to America", "death to Israel" and "revenge, revenge" chants echoed through Tehran's Grand Mosalla on Saturday as thousands of mourners gathered for the start of six days of public funeral ceremonies for Iran's late Supreme Leader Ayatollah Ali Khamenei.Mourners carrying red banners, a symbol associated with calls for revenge, filled the vast religious complex, AFP reported. Iranian authorities estimate between 15 and 20 million people will take part in the ceremonies in Tehran over the next three days.The funeral marks the beginning of a week-long farewell for Khamenei, who ruled the Islamic Republic from 1989 until his death at the age of 86 after being killed in US-Israeli strikes on February 28. The coffin will lie in state until Monday, when a procession will move through Tehran before continuing to Qom on Tuesday, the Iraqi Shia holy cities of Baghdad, Karbala and Najaf on Wednesday, and finally Mashhad on Thursday, where he will be buried.Heavy security has been deployed for what is expected to be Iran's largest public gathering since the funeral of Ayatollah Ruhollah Khomeini in 1989. Roads have been blocked, airspace is expected to be closed, and authorities have stationed water tankers along key routes as temperatures are forecast to exceed 35 degrees Celsius (95 degrees Fahrenheit).Senior Iranian leaders, including Parliament Speaker Mohammad Bagher Ghalibaf, attended the opening ceremony alongside international dignitaries such as Pakistan Prime Minister Shehbaz Sharif and Russian Security Council Deputy Chairman Dmitry Medvedev. Representatives of Hamas, Hezbollah and Afghanistan's Taliban government were also present.The ceremonies are also being closely watched for a possible public appearance by Mojtaba Khamenei, the late leader's son and designated successor, who has not appeared in public since his father's death.