The "Islamic State of Iraq and the Levant" (ISIL) used chemical weapons against Iraqi forces taking part in the operation to recapture Mosul, injuring some security personnel, AFP reported Sunday (April 16th).

ISIL has periodically carried out attacks using chemical weapons, but both the toll and the impact on military operations has been minimal.

"ISIL terrorist gangs tried to block the advance of our forces by using shells filled with toxic chemical material, but the effect was limited," Iraq's Joint Operations Command said in a statement.

The attack on Saturday did not result in any deaths but did cause "limited injuries" among security personnel, the military command said.

The statement said that the forces attacked were part of the massive operation aimed at recapturing the city of Mosul from ISIL, but did not specify if the attack took place in or outside the city.

On Monday, joint Iraqi forces rolled into the Old City area in central Mosul and besieged al-Nouri Mosque where ISIL chief Abu Bakr al-Baghdadi delivered his speech in 2014.

Federal Police Chief Lt. Gen. Raed Shaker Jawdat said that dozens of ISIL elements were killed in violent battles that have been ongoing since dawn Monday.

"Iraq forces have retaken al-Maash Market in the Old City ... and besieged al-Nouri Mosque," Jawdat said in a press conference held in Mosul.

"Battles are underway in alleys, and dozens of terrorists have been killed," he said, noting that the battles are supported by the army’s artillery and international coalition fighter jets.

Meanwhile, the Iraqi Ministry of Defence said that an ISIL leader and his aide were killed in Mosul.

"The military commander in al-Thawra neighbourhood, Bahaa al-Jubury, and his Palestinian aide, Abu Talha, were killed in Sunday's battles," the ministry said in a statement.