Iraqi troops have entered the Karama district of Mosul, their first advance into the city itself after two weeks of fighting in the surrounding area to dislodge so-called Islamic State militants.
Military commanders said that the US-backed offensive to recapture Mosul - the largest military operation in Iraq since the US-led invasion that toppled Saddam Hussein in 2003 - could still take weeks and possibly months.
Troops from the Counter Terrorism Service (CTS) were moving in on Gogjali, an industrial zone on Mosul's eastern outskirts, and could enter it later today, an officer from the US-trained unit told a Reuters correspondent just east of Mosul.
The zone lies about a kilometre from the administrative border of Mosul.
The capture of Mosul would mark the militants' effective defeat in the Iraqi half of the caliphate that Islamic State leader Abu Bakr al-Baghdadi declared two years ago from the city's Grand Mosque.
It is still home to 1.5 million residents, making it four or five times bigger than any other city they seized in both Iraq and Syria.
Other military statements said five villages were taken north of Mosul, where Kurdish Peshmerga fighters are also being deployed, while army units advanced in the south.
Pro-Iranian Iraqi Shia militias joined the fighting on Saturday, aiming to cut the route between Mosul and Raqqa,Islamic State's main stronghold in Syria.
Islamic State militants has been fighting off the offensive with suicide car bombs, snipers and mortar fire.
They have also set oil wells on fire to cover their movements and displaced thousands of civilians from villages toward Mosul, using them as "human shields", UN officials and villagers have said.
"Scorched earth tactics employed by retreating ISIL members are having an immediate health impact on civilians, and risk long-term environmental and health consequences," the UN's Office for the Coordination of Humanitarian Affairs said.