Iran has bolstered its influence over its neighbour in recent years. Iraq's state-sponsored Hashed-al-Shaabi paramilitary network, which is dominated by pro-Iran groups, now wields major political and military sway in the country.

Critics have accused the Hashed of being Iran's armed wing in Iraq, and protesters who took part in a popular uprising in late 2019 blame it for wave of assassinations and kidnappings of activists.

During a religious event on Saturday, Sheikh Hamid al-Yassiri appeared to lash out at the Hashed, without naming it or Iran directly.

Revered Shiite figure "Imam Hussein taught us that whoever is not loyal to his homeland is a traitor and an imposter," Yassiri said.

"All counsel, all voices and positions that come from beyond the borders have nothing to do with the doctrine of Imam Hussein."

The comments sparked the ire of Qais al-Khazali, who heads a powerful Hashed faction known as Asaib Ahl al-Haq.

Khazali in a tweet accused "certain religious figures who hide behind nationalism" of "trying to pass off their projects by linking their ideas to Imam Hussein".

Sistani, the highest religious authority for Iraq's Shiite Muslims, is highly reclusive and rarely breaks his silence to intervene in politics.

In June 2014, he issued a historic edict calling on Iraqis to take up arms against the Sunni jihadists of the Islamic State group who had swept across swathes of the north -- a ruling that spawned the creation of the Hashed al-Shaabi.