Iran reiterated its pledge to punish Israel on Friday at a funeral for seven officers killed in a suspected Israeli airstrike on the Iranian embassy compound in Syria this week.
State television showed demonstrators carrying pictures of those killed and banners with slogans such as "Death to Israel" and "Death to America".
The dead included one of Iran's top soldiers, Brigadier General Mohammad Reza Zahedi, a senior commander in the Islamic Revolutionary Guard Corps (IRGC) who was visiting the Iranian embassy compound in the Syrian capital Damascus on Monday.
"No act of the enemy against the sacred Islamic republic will go unanswered," Major General Hossein Salami, the IRGC commander-in-chief, told the crowd gathered in Tehran. "Our brave men will punish the Zionist regime."
Former Guards commander Mohsen Rezaei, commenting on the possibility of retaliation against Israel, said: "The decision has been made. It will definitely be implemented," according to the semi-official Tasnim new site. He did not elaborate.
The funeral coincided with the annual Quds (Jerusalem) Day, during which Iran stages large state-sponsored pro-Palestinian and anti-Israel rallies nationwide.
The leader of Palestinian militant group Islamic Jihad, Ziad al-Nakhala, took part in the Tehran rally, Iranian media reported.
The airstrike was the boldest, and deadliest attack in a series that have killed Iranian officials in Syria since December.
Iran warned of harsh retaliation, raising the spectre of a wider war and prompting the Israeli armed forces to suspend leave for all combat units on Thursday, a day after they said they were mobilising more troops for air defence units.
Israeli Prime Minister Benjamin Netanyahu said on Thursday his country would harm "whoever harms us or plans to harm us".
In Tehran, the coffins of two of the killed Iranian officers were displayed as people intoned religious mourning chants and waved the Palestinian flag. All seven officers were expected to be buried later on Friday.
Iran's Jerusalem Day rallies are held annually on the last Friday of the Muslim fasting month of Ramadan in support of Palestinians, who want East Jerusalem as the capital of a future state in territories captured by Israel in a 1967 war.
