DAMASCUS, Syria -- At least 41 civilians were being treated Saturday following a suspected poison gas attack by Syrian rebel groups on the government-held Aleppo city in the country's north, according to Syrian state media.

Syrian state TV previously said that 21 people had been injured, but people continued to arrive at a hospital in Aleppo where state TV was airing live.

Doctors told state TV that most of those admitted to hospitals suffered from breathing problems and blurred vision. One doctor said two were in critical condition, including a child. State TV showed footage of medical professionals treating men and women on hospital beds.

Rami Abdurrahman, the head of Britain-based Syrian Observatory for Human Rights, said there was a stench of gas in Aleppo city after projectiles were fired.

Aleppo police chief Essam al-Shali told state TV the projectiles landed in the al-Khalidiya neighbourhood and wind conditions caused gas to spread. State TV later said the gas affected two other areas in the city. There are no deaths, al-Shali said.

Aleppo Gov. Hussein Diab visited the injured at the hospital. He told state TV that a total of 41 people had been admitted and accused rebels of using poisonous gas in the missiles they lobbed at the Aleppo neighbourhood.

An unnamed doctor told the same outlet that a poisonous gas was believed to have been used, but tests were needed to determine what kind.

Earlier, state media said it was believed to be chlorine.

One patient said a foul smell filled the air after projectiles were lobbed.

"There are often missiles on the city but this is the first time we smelled such a smell," the patient said without giving his name.

Aleppo has come under rebel attack in recent weeks, with missiles falling inside the city. The government has responded with counter attacks on rebel-held areas in the Aleppo countryside.

In the absence of independent monitors, it is difficult to corroborate gas attacks. But both sides of the conflict have accused each other throughout the war of using poison gas.

A joint team from the United Nations and the Organization for the Prohibition of Chemical Weapons accused Syria's government of using chlorine gas in at least two attacks in 2014 and 2015, and the nerve agent sarin in an attack in April 2017 in the town of Khan Sheikhoun that killed about 100 people. The U.S. launched a series of strikes on Syrian government sites in retaliation for the attack in Khan Sheikhoun.

The UN-OPCW team also accused the Islamic State extremist group of using mustard gas twice in 2015 and 2016.

The government accused rebels of using gas in a 2013 attack on Khan al-Assal, a village southwest of Aleppo city, that killed 25 people.

Associated Press Sarah El Deeb contributed to this report from Beirut.