Fighters loyal to Iraq’s populist Shiite cleric Moqtada Al Sadr on Tuesday said they were stationed across the country following alleged threats to holy cities.
Security officials denied the claims.
Footage circulated on social media showed armed men in masks setting up security checkpoints and searching cars in the capital Baghdad as well as the two holy cities of Karbala and Najaf.
Mr Al Sadr's adviser Saleh Al Iraqi said: "We have received almost certain information that there is an agreement between the Baathists, ISIS and some infiltrators to attack holy sites."
“The targeting will not be on Shiite shrines, so to speak, but it is designed to spread discord and chaos, so we want to draw your attention to this,” Mr Al Iraqi, who is known as "Al Sadr’s minister", said on Twitter.
He praised the posting of militias.
But two security officials told The National there were no threats against any religious sites in the country.
“Saraya Al Salam [Al Sadr's militia] did not co-ordinate with the security forces on the deployment as they claimed,” the officials said.
Some of the fighters were still in Mr Al Sadr's strongholds like Sadr City and Palestine Street in eastern Baghdad.
There was no official clarification on whether government forces had co-ordinated with the militia.
A lawmaker told The National the move was a "mere show of force" by Mr Al Sadr after he expressed a desire to run for the post of prime minister in the coming elections.
Several Sunni and Shiite politicians have rejected Mr Al Sadr's efforts to take the post, given his militia’s role in Iraq’s sectarian conflicts that occurred between 2005 and 2007.
Mr Al Sadr is known to be a nationalist who opposes the involvement of both the US and Iran in Iraq.
The populist cleric has always been viewed by the US as a wild card in Iraq’s turbulent politics, which is often driven by sectarian interests.
Officials in Washington have described him as “the biggest security threat in Iraq.”
His political bloc scored a surprise victory in the 2018 nationwide elections by promising to fight corruption and improve public services.
Iraqi Prime Minister Mustafa Al Kadhimi said on Monday night his government would not "tolerate any transgressors".
“We will not give up on state-building and its prestige … building is not done by encroaching on religious and national symbols, striking institutions, and blocking roads, but with state support," he said on Twitter.
Iraq’s military and police dislodged ISIS in 2017.
The group had taken over about a third of the country with the help of both a US-led coalition and the Popular Mobilisation Forces, many of which are linked to political groups.
The Popular Mobilisation Forces was later formally integrated into Iraq’s official security structure, and militias officially severed ties with their political wings although informal links remain.