The patients, who are being treated in hospital in nearby Irbil, are "showing clinical symptoms consistent with an exposure to a blistering chemical agent," said Robert Mardini, the organization's regional director for the Middle East.
The five children, three women and four men have symptoms that include blisters, coughing, redness in the eyes, irritation, and vomiting.
"The use of chemical weapons is absolutely prohibited under international humanitarian law. We are deeply alarmed by what our colleagues have seen, and we strongly condemn any use of chemical weapons, by any party, anywhere," ICRC's Mardini said.
The Organization for the Prohibition of Chemical Weapons released a similar statement on Sunday, stating that it's "seriously concerned" over the alleged use of chemical weapons in Mosul.
"Parties to the Chemical Weapons Convention deem the use of chemical weapons by anyone under any circumstances as reprehensible and wholly contrary to the legal norms established by the international community," the organization said.
Dr. Lawan Miwan, head of Emergency Hospital in Irbil, told CNN his hospital is treating two cases with symptoms consistent with exposure to a toxic chemical agent.
CNN talked with two residents of east Mosul who reported smelling "something strange," "like a chemical agent," or "mustard gas" following mortar attacks on eastern Mosul on Wednesday and Thursday. The residents said the attacks came across the Tigris River from western Mosul.
ICRC spokeswoman Sara Alzawqari said the first three cases were brought to the hospital on Wednesday, followed by another four Thursday. Five victims arrived in somewhat better medical condition on Friday. All are victims of the same attack, Alzawqari said.
The World Health Organization has responded to the reported use of chemical weapons agents in eastern Mosul, activating an emergency response plan to treat those who may be exposed to the highly toxic chemicals, the WHO said Friday.
Two Iraqi security officials near Mosul could not confirm nor deny the incidents to CNN.
ISIS has used chemical weapons on numerous occasions in Iraq and Syria, including in the battlefield in northern Iraq, according to Iraqi and US officials.
This is believed to be the first such attack in Mosul since the October start of the offensive to retake Iraq's second most populous city from ISIS control .
Iraq: Coalition strike kills 6 ISIS leaders
Six ISIS military leaders were killed during a US-led coalition airstrike in western Mosul, the Iraqi Joint Operations Command said.
Coalition aircraft destroyed an ISIS headquarters that was a command center for the so-called "Soldiers of the Caliphate."
Abdul Rahman al-Ansari, a Saudi Arabian and the leader of the Soldiers of the Caliphate is among those believed dead, the command center said.
Another airstrike killed the man who led ISIS's booby-trapping operations in Ninevah province, authorities said.
Refugee crisis grows
The number of Iraqi refugees fleeing western Mosul shot up to more than 46,000 by Friday morning, the Ministry of Migration and Displaced in Iraq said.
At least 14,000 civilians fled Mosul on Thursday alone, the ministry said.
"All we've had for the last month is bread and water" said a Mosul resident named Ahmed, who declined to give his full name for fear of reprisals. He came with his wife and five children from the Ma'moun neighborhood in southwestern Mosul.
"We left when mortar rounds started hitting around our house. We couldn't stay any longer," said his wife, Mariam.
The number of refugees is expected to increase as the battle for western Mosul closes in on the heart of that side of the city, migration ministry head Saif Sabah said.
Sabah told CNN that officials have seen "greater and higher numbers" of civilians fleeing western Mosul than from the eastern side of Mosul.
The number of civilians are "double and even triple per day to that compared to eastern Mosul," Sabah said. "We are only 13 days in (to heavy fighting in that part of the city) .... and the numbers have exceeded our expectations."