Hashemi, 47, was a specialist in jihadist movements and had developed a vast network of top decision makers, armed groups and rival parties, often mediating among them.

He was shot dead outside his Baghdad home by gunmen on motorcycles on July 6 last year, leaving behind a wife, three sons and a daughter.

Nobody has ever been arrested for the killing.

Journalists were among those who attended Tuesday's ceremony in Baghdad's Tahrir Square to remember a man whose murder shocked the country.

Participants held pictures of Hashemi and lit candles in honour of the researcher.

Alongside being an expert on Sunni extremism in Iraq, he had become outspoken against powerful Shiite armed actors.

Hashemi's support for popular protests that erupted in 2019 against a government seen as too close to Iran infuriated Tehran-backed Shiite factions in Iraq's Hashed al-Shaabi military network.

"A year has passed since this heinous crime and the government has been unable to find the killers," said Majid Al-Khalidi, a journalist.

A colleague called Hashemi the "best security analyst Iraq has ever known".

An interior ministry official at Tuesday's ceremony said "no effort will be spared" in the hunt for the killers.

Last month, a Hashed al-Shaabi commander arrested as a suspect in the murder of a pro-democracy activist was released, sparking renewed debate about the authorities' ability to contain Shiite armed groups, which control lucrative asset streams.