Iraqi forces launched an operation on Tuesday to secure the border with Syria, the country's state news agency said.
The 600-kilometre boundary between the countries is controlled by a variety of forces, including the Iraqi military, Syrian Army, US-backed Kurdish forces, Iran-backed militias and anti-government rebels.
It is a flashpoint of tension between Iran-backed groups and the US, exacerbated by ISIS incursions and Turkish pressure on Kurdish rebel groups.
“The military’s three components are taking part in the operation, they are the border forces command, the Popular Mobilisation Forces (PMF) and the army’s aviation sector,” Lt Gen Hamid Al Husseini told Iraq’s News Agency.
The PMF, a coalition of militia groups, was formed in 2014 to fight ISIS alongside the Iraqi Army. It was formally incorporated into the Iraqi Security Forces in 2017, but many of the groups are backing by Iran.
For years the Iraqi Army has been attempting to clear the desert bordering Syria of ISIS, in a bid to combat the group’s remaining sleeper cells.
Despite the government announcing victory over ISIS in 2017, remnants and cells of the group still regularly stage hit-and-run attacks or plant explosives across the country.
They have also tried to curb drug smuggling and other illegal activities at the border.
Several military officials say Iraq has increased the use of high-tech thermal cameras and observation balloons.
Its military finds itself in the difficult position of needing to co-ordinate with state paramilitaries that include Iran-backed groups that are facing off with Israel and the US and transferring weapons and personnel across the frontier.
Israel this year launched air strikes against Iranian-linked targets including the Revolutionary Guards commanders as Tel Aviv has put pressure on allies of Iran and of Syrian President Bashar Al Assad.
In June, Washington said it carried out air strikes against those militias stationed near the Iraq-Syria border as its troops have come under drone attacks in Iraq.
A Pentagon spokesman said the strikes were aimed at "operational and weapons storage facilities" at three locations.
US President Biden was clear he would act to protect American personnel, he said.