Islamic State militants are now almost surrounded in their last major urban stronghold in Iraq.
Iraqi special forces have recaptured six districts of eastern Mosul, expanding the army's foothold in the Islamic State stronghold a day after its leader told his jihadist followers there could be no retreat.
An officer in the elite Counter Terrorism Service said CTS troops had launched a major operation against the militants, who are now almost surrounded in their last major urban stronghold in Iraq.
CTS special forces took over the neighbourhoods of Malayeen, Samah, Khadra, Karkukli, Quds and Karama, a military statement said, inflicting heavy losses on the militant fighters and raising the Iraqi flag over buildings.
One special forces officer said the CTS units may try to push all the way to the Tigris river, which runs through the centre of Mosul.
Iraqi television footage from the east of the city showed heavy palls of grey smoke rising into the sky.
Iraqi regular troops and special forces, Shi'ite militias, Kurdish peshmerga fighters and other groups backed by US-led air strikes launched a campaign nearly three weeks ago to retake Mosul.
Winning back the city would crush the Iraqi half of a crossborder caliphate declared by Islamic State leader Abu Bakr al-Baghdadi from a Mosul mosque two years ago.
Mosul is still home to nearly 1.5 million people, who risk being caught up in brutal urban warfare. The United Nations has warned of a potential humanitarian crisis and a refugee exodus, although Iraqi officials say Islamic State is holding the civilian population as human shields.