Iraqi prime minister Haider al-Abadi has congratulated Iraqi fighters on "this big victory in Mosul" even as fighting continues in Mosul's Old City.
Iraqi forces are about 250 metres from the Tigris River and facing increasingly brutal resistance from Islamic State (IS) fighters.
Mr al-Abadi spoke during a press conference in Baghdad, less than a week after he declared an end to IS's self-styled caliphate after Iraqi forces achieved an incremental win by retaking the landmark al-Nuri Mosque in the Old City.
His remarks come on the three-year anniversary of IS leader Abu Bakr al-Baghdadi's sermon at the al-Nuri Mosque, from where he declared an Islamic caliphate.
Iraqi forces launched the operation to retake Mosul, the country's second largest city, in October.
IS overran Mosul in a matter of days in 2014.
Mr al-Abadi said: "Praise be to God, we managed to liberate (Mosul) and proved the others were wrong, the people of Mosul supported and stood with our security forces against terrorism."
The Iraqi PM added that he has given instructions to rebuild and stabilise areas of the city already freed from the militant group.
Lt Gen Abdel Ghani al-Asadi, of Iraq's special forces, said earlier in the day that Iraqi forces are yards away from the Tigris River, in the western half of Mosul.
The Tigris divides the city roughly into its western and eastern half, which was liberated from IS militants back in January.
IS militants who remain trapped in just a few hundred meters of territory in the Old City are now in a "fight to the death," Lt Gen al-Asadi said, adding that IS fighters are increasingly resorting to suicide bombings.
He said he expects the fighting to get even heavier as they are pushed closer to the river.
Iraqi forces marked a significant victory this week when the Rapid Response Division retook Mosul's main hospital complex on the city's western side.
The building that once held the city's best medical facilities now sits devastated by the fight.
For weeks, a handful of IS snipers perched in the main hospital's top floors held back hundreds of Iraqi forces.
At the height of the extremists' power, they held nearly a third of Iraq.