Iraqi forces made major gains in the six months since launching the operation to retake Mosul, but the battle for Iraq's second city and the war against the Islamic State group are far from over.
Some 400,000 people are believed to have been trapped in western Mosul with United Nations camps filling up with people fleeing the violence.
Battles are now most intense around Mosul's densely populated and narrowly structured Old City district, where police forces cautiously approach the grand mosque where IS supreme leader Abu Bakr al-Baghdadi declared the establishment of the group's rule.
They also announce that the targeted location was in fact a "fighting position" for Syrian Democratic Forces, who are allies in the US mission to fight the Islamic State. The soldiers are from C Battery, 2nd Battalion, 319th Airborne Field Artillery Regiment.
The Iraqi counterterrorism service and federal police are pressing more deeply into the dense, urban terrain along the Euphrates River and the old part of the city, Dorrian said, while elements of the Iraqi army continue clearing territory to the north and west of the city center.
While the type of poison used was still being investigated, the attack followed another apparent use of weaponized gas on Saturday when ISIS militants launched a rocket filled with what was believed to be chlorine at Iraqi military positions.
According to the statement, there are still some 500,000 people trapped in their homes in the IS-controlled neighborhoods in the western side of Mosul, including 400,000 in the densely populated old city center.
The camp, like other facilities in western Mosul, is supplied by road from Erbil, some 80 km (50 miles) to the east, in the autonomous Iraqi Kurdistan region where aid agencies are based.
The Observatory called on the Iraqi army and allies "to abide by global humanitarian law and take the necessary steps to reduce the danger of Daesh on the safety of civilians".
"When we were playing, they were watching us and some of them carried weapons, and they prevented us from wearing foreign teams' uniforms", said Osama Ali Hamid, a 26-year-old player wearing a Borussia Dortmund jersey.
"There's still another significant number of areas within Iraq that will. need to be cleared of Daesh, and. the Iraqi security forces are getting themselves ready for that eventuality - they know that it's coming", he said.
South Korea: North Korea missile test ends in failure
Asked if he was confident that China will pressure North Korea in a meaningful way, McMaster replied, "We'll see what happens". Another missile test from Sinpo failed earlier this month, when the rocket spun out of control and plunged into the ocean.