Several reports in the last few days suggest that the Islamic State is now recruiting in southern Afghanistan, the spiritual heart of the Taliban and the site of fierce combat between U.S. troops and insurgents in recent years. At the center of it: a former Guantanamo Bay, Cuba, detainee who led a Taliban unit before the U.S. sent forces into the country in 2001.

His name is Mullah Abdul Rauf, Afghan officials told the Associated Press on Monday. He is believed to operating in Helmand province, where coalition troops withdrew in October, according to a tribal leader in Sangin district.

“People are saying that he has raised black flags and even has tried to bring down white Taliban flags in some areas,” the tribal leader, Saifullah Sanginwal, told the AP. “There are reports that 19 or 20 people have been killed” in fighting between the Taliban and the Islamic State group, he added. Those reports have not been confirmed by Afghan authorities.

Gen. Mahmood Khan, the No. 2 commander of the Afghan army in Helmand, also told the AP that Rauf had representatives fanning out across numerous Helmand districts within the past week.

The situation creates some complicated dynamics between the Islamist groups. The AP reported that the Taliban has told Afghans in Helmand not to contact Rauf or his men. The Wall Street Journal noted Sunday that a number of Afghan and Pakistani militants recently announced their devotion to the Islamic State, potentially setting the stage for battles not only between the Islamic State and Afghan troops, but also between the Islamic State and the Taliban.

Rauf is also known as Abdul Rauf Aliza and Maulvi Abdul Rauf Khadim. According to a military document released by the anti-secrecy group WikiLeaks, he turns 34 in February and was listed as detainee 108 at Guantanamo Bay. He was transferred to Afghanistan’s control in 2007.

The report on him released by WikiLeaks said he was associated with several known Taliban commanders, but claimed to be a low-level soldier. In interviews with U.S. officials,  he was cooperative, but his responses were vague or inconsistent when asked about the Taliban leadership, according to the report. Nonetheless, Rauf was assessed not to be a threat, and was recommended for transfer out and continued detainment in another country.

“Detainee was in a position to have extensive knowledge of the opium trade in Afghanistan and could identify the individuals in the criminal organizations that were working with both the Taliban and the Northern Alliance in the opium trade,” the recommendation said. “Transfer to the control of another country for continued detention.”

As the Long War Journal has pointed out, Rauf was eventually released and became a shadow governor in the southern Afghan province of Uruzgan. He was never a foot soldier, but a member of Taliban leader Mullah Omar’s elite mobile reserve force before the attacks on Sept. 11, 2001, Newsweek reported in 2011. He was believed to have a following of fighters in Helmand and neighboring Kandahar province.