A senior leader of the Islamic State group has been killed during a military operation by the Iraqi forces in the city of Tikrit, local media reported Monday. Abu Maria, a self-declared governor of ISIS for al-Hajaj and Albu-Tema areas in Iraq was killed by Iraqi troops on Sunday near the Ajeel oil field close to Tikrit, which is located about 87 miles northwest of Baghdad, Iraqi News reported.

“Today, a force from the Omaya al-Jabbara Battalion has managed to kill the ISIS governor (Wali) of al-Hajaj and Albu-Tema areas, known as Abu Maria, along with his key assistant near the area of Ajil oilfield in northeast of Tikrit city,” Iraqi News quoted an anonymous source as saying. “The terrorists were heading towards the district of al-Hawija.”

The source also said that the operation was based on intelligence received from the residents of the local area near Ajeel oil field.

Tikrit has been under ISIS control since June. On March 31, Iraqi Prime Minister Haidar al-Abadi declared that Iraqi troops aided by Shiite paramilitaries had driven ISIS militants out of the city. The U.S. Department of Defense also said at the time that it could confirm Iraqi security forces’ “advancement into Tikrit to liberate the city center as well as other parts of the city” from ISIS.

However, subsequent reports claimed that ISIS fighters were still active in central Tikrit, and that the city was not completely liberated.

Meanwhile, the U.S. government announced last week that the U.S. and coalition military forces continued to attack ISIS positions in Syria and Iraq. According to officials, eight airstrikes were conducted in Syria on Sunday, while nine airstrikes were conducted against the extremist group in Iraq on the same day.