Iraqi special forces are now less than 1.5km from the eastern outskirts of Mosul and are preparing to enter the city held by Islamic State fighters.
Hundreds of Counter-Terrorism Service (CTS) troops entered Bazwaya, the last village before the city limits, after launching a dawn assault on Monday.
A BBC correspondent travelling with them says there was some resistance, with car bombs targeting the convoy.
Units of the army's ninth division are meanwhile advancing from the south.
Earlier, the military announced the start of an operation to retake the side of Mosul east of the River Tigris, which flows through the city.
The BBC's Ian Pannell, who is with a CTS unit, says the assault on Bazwaya, about 3km (1.9 miles) from Mosul, began early on Monday.
Hundreds of troops in heavily-armoured Humvees, together with tanks and bulldozers, advanced on the village, supported by US-led coalition air strikes, our correspondent adds.
Within hours the head of the Iraqi military's Nineveh Operations Command, Lt-Gen Abdul Amir Yarallah, announced that they had entered Bazwaya and raised the Iraqi flag.
Our correspondent says that a column of troops is now probing different parts of Mosul's outskirts, as commanders make a plan about where to go next.