In a stunning development that threatens to further destabilize the Middle East, Iran has deployed an elite unit of its Revolutionary Guard to help the Iraqi government take on ISIS, the Sunni militant group that has seized several areas in the northern part of the country.

Two battalions of the Quds Forces are already making progress in their fight against the Islamic State of Iraq and Syria, or ISIS, the Wall Street Journal reported. The militant group took control of Saddam Hussein’s hometown of Tikrit on Wednesday, but Revolutionary Guard and Iraqi troops overtook 85 percent of the city on Thursday, Iraqi and Iranian security forces told the paper.

Iran, which is dominated by Shiites, has close ties to Iraq’s Shiite-led government. Iranian President Hassan Rouhani called ISIS “an extremist, terrorist group that is acting savagely” during an appearance on state television, Al Jazeera reported. "For our part, as the government of the Islamic Republic of Iran ... we will combat violence, extremism and terrorism in the region and the world."

The Iranian military is considering shifting troops fighting in Syria, where forces are supporting Syrian President Bashar Assad’s government, to Iraq if the deployment of the Quds Forces doesn’t make any progress in the latest offensive.

The Times of London said 150 members of the Quds Forces are in Iraq, where ISIS militants seized Mosul, Iraq’s second-largest city, earlier this week.

Meanwhile, ISIS continue to vow that it would soon march on Baghdad.

“'Our final destination will be Baghdad, the decisive battle will be there,' that’s what their leader kept repeating," a tribal figure near Tikrit relayed to Reuters.