Iraqi forces have retaken more than a third of west Mosul from the Islamic State group, a commander said, as Baghdad's troops fought Sunday to advance deeper into the city.
Iraqi forces launched the operation to recapture west Mosul -- the most populated urban area still under IS control -- on February 19, retaking a series of areas as they advanced up from the south.
Officers have said that jihadist resistance is weakening, but tough fighting -- including in the Old City, a warren of narrow streets and closely-spaced buildings where hundreds of thousands of civilians may still reside -- remains ahead.
"Around more than a third of the right bank (west Mosul) is under the control of our units," Staff Major General Maan al-Saadi of the elite Counter-Terrorism Service told AFP.
CTS forces were battling IS inside the Mosul al-Jadida and al-Aghawat areas in west Mosul on Sunday, said Saadi, adding that he expected the fighting there to be completed in the coming hours.
And Iraq's Joint Operations Command (JOC) said that forces from the Rapid Response Division, another special forces unit, and the federal police were attacking the Bab al-Toub area on the edge of the Old City.
But the process of advancing in Mosul is laborious, Saadi said.
"We are not able to leave pockets (of jihadists) behind us; therefore, the advance includes taking control of areas and searching and clearing them and security checks on the citizens present, then the continuation of the advance," he said.
- 'Not easy' -
The jihadists are "still relying on explosives-rigged vehicles and suicide bombers and snipers" and units that aim to slow the Iraqi advance, Brigadier General Yahya Rasool, the spokesman for the JOC, told AFP.
"The battle is not easy... we are fighting an irregular enemy who hides among the citizens and uses tactics of booby-trapping, explosions and suicide bombers, and the operation is taking place with precision to preserve the lives of the citizens," Rasool said.
But IS resistance "has begun to weaken in a big way," he said.
The battle against IS inside west Mosul is being spearheaded by CTS and the Rapid Response Division, the latter of which is working with the federal police.
Outside Mosul, Iraqi army forces and pro-government paramilitaries are operating against IS to the west of the city.
On Saturday, the Hashed al-Shaabi -- an umbrella organization for paramilitary groups that is dominated by Iran-backed Shiite militias -- announced the discovery of a large mass grave northwest of Mosul.
The Hashed said the grave contained the remains of around 500 people killed by IS at the Badush prison, a figure that could not be independently confirmed, but which was in keeping with accounts from Human Rights Watch and the United Nations.
According to HRW, IS gunmen executed up to 600 inmates from the prison on June 10, 2014, forcing them to kneel along a nearby ravine and then shooting them with assault rifles, an account also contained in a U.N. report.
IS overran large areas north and west of Baghdad in 2014, but Iraqi forces backed by U.S.-led air strikes and other support have since retaken most of the territory they lost.