"Army helicopters carried out a series of attacks against targets in the Old City," one witness said, noting that militia vehicles "continued to arrive" in the historical center of Mosul throughout Friday.
"Only one family was able to get out of the Old Town area for today," he said.
Residents of the western part of Mosul report that members of terrorist groups continued to hide in the cellars of the residential buildings of the Old City, taking civilians as hostages.
On Monday, Iraq's Prime Minister Haider al-Abadi announced that Iraqi security forces had finally liberated Mosul, the second largest Iraqi city, after months of fighting against the Islamic State. The city was seized by the IS three years ago.
On Tuesday, the commander of US-led anti-IS coalition, Lt. Gen. Stephen Townsend, said that the cleanup of Iraqi Mosul from the militants would take several more weeks.