Iraqi forces have for the first time entered the eastern outskirts of Mosul, as they attempt to drive Islamic State (IS) militants from the northern city.
A BBC correspondent travelling with the Counter-Terrorism Service troops says they are facing very stiff resistance.
Rocket-propelled grenades and small arms fire are being directed at them.
Iraqi Prime Minister Haider al-Abadi has told IS militants dug in inside Mosul, which they have held since June 2014, to "surrender or die".
Speaking at the Qayyarah airbase south of the city on Monday, Mr Abadi declared that government forces were approaching from all angles and would "cut off the head of the snake".
About 50,000 Iraqi security forces personnel, Kurdish Peshmerga fighters, Sunni Arab tribesmen and Shia militiamen are involved in the offensive to drive IS militants out of their last major urban stronghold in the country.
Before the operation began on 17 October, there were believed to be between 3,000 and 5,000 militants remaining in Mosul, along with up to 1.5 million civilians.
More than 17,900 residents have fled so far and, according to the UN's worst-case scenario, as many as 700,000 others could follow suit.