Roads have been closed off in large parts of central Tehran, where the Imam Khomeini Mosque is located.
The crowds began gathering during the night, waiting for the supreme leader's Friday prayer, the first in nearly five years.
The Ayatollah addresses his speech directly to his "Palestinian and Lebanese brothers" and devotes a large part of his speech to guaranteeing Iran's support to the allied militias in the region. A segment of the prayer is therefore held in Arabic.
Khamenei defends Hamas' large-scale terrorist attacks against Israel nearly a year ago, as well as Iran's missile rain against Israel on Tuesday.
"Death to Israel", the thousands of supporters gathered outside the mosque chant on several occasions.
The Ayatollah himself makes direct threats against Israel, which he says "will not survive for long".
Turbulent situation
According to the AFP news agency, a weapon is placed beside Khamenei.
The sermon is held in a particularly turbulent situation for Iran and its allied militias in the region.
Last Friday, Hezbollah's long-time leader Hassan Nasrallah was killed in a bombing raid against al-Dahiya in southern Beirut. Now, reports are circulating that his expected successor Hashem Safieddine was the target of another Israeli attack in the area.
The supreme leader's prayer is held after a memorial ceremony for Nasrallah and the high-ranking General Abbas Nilforushan from Iran's Revolutionary Guard, who was also killed in Israel's attacks on Lebanon.
No clear plans for further revenge or hints about how Iran will act in the conflict going forward are mentioned in the sermon, which primarily seems to aim to show support for the allies in the region.
Waiting for revenge?
According to reports in the media, the 85-year-old Ayatollah was moved to a "safe location" after the news of Nasrallah's death last weekend.
Iran's Revolutionary Guard has announced that Tuesday's missile attack against Israel was retaliation for, among other things, Nasrallah's and Nilforushan's deaths. Israel has since promised a "painful" response to the attack.
The last time Khamenei led the Friday prayer was when the commander of the Revolutionary Guard, Qasem Soleimani, was killed in an American drone attack in Baghdad, Iraq in 2020, and Iran subsequently mistakenly shot down a Ukrainian passenger plane.
