Iraqi forces battled their way along two streets that meet in the heart of Mosul's Old City on Friday, and said they aimed to open routes for civilians to flee Islamic State's last stand there.
U.S.-trained urban warfare units are leading the fight in the maze of narrow alleyways of the Old City, the last district in the hands of the Sunni Islamist insurgents.
Iraqi authorities are hoping to declare victory in the northern Iraqi city in the Muslim Eid holiday, which marks the end of the fasting month of Ramadan, during the next few days.
Military analysts say government troops' advance will gather pace after Islamic State fighters blew up the 850-year-old al-Nuri mosque and its famous leaning minaret on Wednesday.
Islamic State retaliated with a triple bombing on a neighbourhood in east Mosul, the other side the Tigris River.
The attack was carried out by three people who detonated explosive belts, killing and wounding an unspecified number of people, according to a military statement.
Destruction of the mosque gives troops more freedom in attack as they no longer have to worry about damaging the ancient site.
It was in the al-Nuri mosque that Islamic State's leader, Abu Bakr al-Baghdadi, proclaimed its "caliphate" over parts of Iraq and Syria three years ago.
A U.S.-led international coalition is providing air and ground support in the 8-month-old offensive to drive the militants from their de facto capital in Iraq.
A map published by the Iraqi forces media office showed the elite Counter Terrorism Service pushing along al-Faruq Street, from north to south, and Nineveh Street, from east to west.
The two roads cross in the centre of the Old City. When the troops reach this point, they will have isolated the remaining IS fighters in four separate pockets.
"The aim is to open ways for civilians to evacuate. We give them indications by lousdspeaker when it's possible," an Iraqi military spokesman told Reuters by phone.
Some 7,000 civilians were brought out of the Old City this week, the Iraqi state news website said. Several street intersections were seized during the day.
Reuters journalists in Mosul saw people reaching safety. Some were injured and some had been carried on army humvees to rear positions where they were given bananas, biscuits and water.
"The army's 16th division evacuated us," said a man who had fled with his wife and 15-day-old baby.
"God bless them," said another man, who was limping.
Doctors Without Borders (MSF) reported an influx of wounded to its trauma clinic in the west of the war-torn city on Friday morning.
"This ... is yet another example of the horrific suffering and indiscriminate violence suffered by civilians, including women and children," said Jonathan Henry, MSF Emergency Coordinator for West Mosul, in a statement.
More than 100,000 civilians, of whom half are children, are trapped in the crumbling old houses of the Old City, with little food, water or medical treatment.
Aid organisations say Islamic State has stopped many from leaving, using them as human shields. Hundreds of civilians fleeing the Old City have been killed in the past three weeks.
The Iraqi government once hoped to take Mosul by the end of 2016, but the bloody campaign has dragged on as the militants reinforced positions in civilian areas, launched suicide car and motorbike bombs, laid booby traps and kept up barrages of sniper and mortar fire.
The military said it had defused dozens of booby traps as troops advanced on Friday.
The area still under IS control is about 2 square kilometres (0.77 square miles) in extent, alongside the western bank of the Tigris, which bisects Mosul.
The fall of Mosul would mark the end of the Iraqi half of the militants' "caliphate" as a state structure, but Islamic State would remain in control of large areas of both Iraq and Syria.
Islamic State posted a video online showing the remaining square base of the mosque's leaning minaret amid a mountain of rubble, with wrecked cars nearby.
The destruction caused anger and grief for Mosul's people, who affectionately call the tower al-Hadba, or "the hunchback".
Islamic State's black flag had been flying on the 150-foot (45-metre) minaret since June 2014. Iraqi Prime Minister Haider al-Abadi said the militants' decision to blow it up was an admission of defeat.
Baghdadi has left the fighting in Mosul to local commanders and has been assumed to be hiding in the Iraqi-Syrian border area. There has been no confirmation of Russian reports over the past week that he has been killed, and officials in the region are sceptical.
"We don't have any concrete evidence on whether or not he's dead either," U.S. Army Colonel Ryan Dillon, spokesman for the international coalition battling Islamic State, told a Pentagon briefing.
In Syria, the insurgents' "capital", Raqqa, is nearly encircled by a U.S.-backed Kurdish-led coalition.
"We certainly know that if he is still alive, we expect that he is not being able to influence what is currently happening in Raqqa or Mosul or overall in the ISIS (Islamic State) as they continue to lose their physical caliphate," Dillon said.
U.S. intelligence officials say Islamic State has moved most of its leaders, along with its online propaganda operation and its limited command and control of attacks in Europe and elsewhere, to Al Mayadin in eastern Syria's Deir al Zour province.
