Iran has held a state funeral service for around 60 people, including its military commanders, killed in its 12-day conflict with Israel, after Tehran's top diplomat condemned Donald Trump's comments targeting Supreme Leader Ali Khamenei as "unacceptable".

The state funeral proceedings in the capital, Tehran, for 60 nuclear scientists and military commanders killed in Israeli strikes began at 8:00 am (0430 GMT) at Enghelab Square on Saturday.

Iranian President Masoud Pezeshkian, as well as other senior government officials, also attended the event.

Images showed coffins draped in Iranian flags and bearing portraits of the deceased commanders in uniform near Enghelab Square in central Tehran.

It will be followed by a funeral procession to Azadi Square, about 11 kilometres across the sprawling metropolis.

Mohsen Mahmoudi, head of Tehran's Islamic Development Coordination Council, vowed it would be a "historic day for Islamic Iran and the revolution".

Among the dead is Mohammad Bagheri, a major general in Iran's Revolutionary Guards and the second-in-command of the armed forces after the Iranian leader.

He was buried alongside his wife and daughter, a journalist for a local media outlet, all killed in an Israeli attack.

Nuclear scientist Mohammad Mehdi Tehranchi, also killed in the attacks, will be buried with his wife.

Revolutionary Guards commander Hossein Salami, who was killed on the first day of the war, will also be laid to rest after Saturday's ceremony, which will also honour at least 30 other top commanders.

Of the 60 people who are to be laid to rest after the ceremony, four are children.

Iran says more than 600 people, mostly civilians, were killed in Israeli attacks on Iran.

Israel states that it lost 28 people and that hundreds of properties were damaged in Iranian retaliatory strikes on Israel.