Fighting rages as nearly 1,000 treated for breathing problems following sulphur plant fire south of key Iraqi city.

At least two Iraqi civilians have died and nearly a 1,000 are being treated for breathing problems from toxic fumes released from a burning sulphur plant near Mosul, as fighting around the key city continued for a sixth day.

ISIL fighters are accused of setting the sulphur plant ablaze on Thursday during fighting around al-Mishraq, which is south of Mosul, accoring to US officials and local residents.

Hundreds of people were admitted to the nearby Qayyara central hospital with respiratory problems since Friday, hospital director Abdul Salam Jabbouri told Reuters news agency. No deaths had been reported at the hospital.

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The blaze released toxic fumes seen and felt by residents in the area and, early on Saturday, by military forces and reporters around Qayyara.

“We have had every type of person come in with breathing problems and burning eyes – children, adults, policemen, soldiers,” said Jabbouri. “Daesh [ISIL] set the sulphur on fire so nobody can come near them.”

An estimated 30,000 fighters, including the Iraqi army, Kurdish Peshmerga, Sunni tribal fighters and the Popular Mobilisation Forces – Shia militias that now have official status from Baghdad – are taking part in the Mosul campaign, which is backed by US-led coalition air strikes.

Iraqi commanders have told Al Jazeera an estimated 6,000 ISIL fighters are inside Iraq’s second-largest city.

A cloud of white smoke blanketed the region to the north, where the sulphur factory is located, mingling with black fumes from oil wells that were torched as well.

US officials said coalition forces at the nearby Qayyara airfield – the main hub to support Iraqi-led operations to retake Mosul – are wearing protective masks.

“The winds have actually shifted south, so as a precautionary measure the troops at Qayyara West have donned their personal protective equipment – continuing their operations at this point in time,” an official said on Saturday.

Iraqi state TV said the fire was put out Saturday.

Al Jazeera’s Imran Khan, reporting from Erbil, said there was confusion over who was responsible for the blaze at the plant.

“Nobody really knows what is going on, whether it was a coalition air strike, Iraqi armour, or ISIL suicide bombing,” he said.

“Because of the constant change in wind directron, the entire area is becoming very dangerous. A lot of soldiers are wearing gas masks and the government is warning residents. While the fire is under control, there is smoke in the air and that is likely to cause health problems.”

Operation Inherent Resolve – the official name of the US-led anti-ISIL coalition – said it had provided more than 24,000 protective chemical masks to Iraqi security forces and the allied Kurdish Peshmerga fighters during training for the Mosul offensive.

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“Daesh [Arabic acronym for ISIL] blew up the sulphur plant two days ago and that has led to the deaths of two people among the civilians in nearby villages,” Iraqi General Qusay Hamid Kadhem told AFP news agency.

Kadhem admitted the toxic fumes were having an impact on operations: “Of course, this is affecting our planned progress.”

In an examination room at Qayyara hospital, a baby, suffering from inhalation of sulphur fumes, screamed and coughed on Saturday as his father held an oxygen mask over his face, according to Reuters.

Most patients have been given oxygen and told to stay away from areas with high sulphur concentration, according to medical aide Saddam Ahmad, who was wearing a surgical mask to protect him from the fumes.

“We’ve had so many patients since yesterday that we’re almost out of oxygen,” Ahmad said.

Ali Ahmad Khalaf, 38, who lives in a nearby village, said he had moved his family to Qayyara to escape the fumes.

“The sulphur is very dangerous,” said Khalaf, wearing a surgical mask and a traditional dishdasha robe. “Daesh just wants to kill us.”

Standing nearby, Bassam Qazi overheard Khalaf and said: “I saw an old man who had choked and died from the smoke.”

Hours after the capture of the key town of Bartella, some 15km east of Mosul’s outskirts, the Iraqi army launched on Saturday a new offensive to retake the southeast district of Hamdaniya, according to Al Jazeera’s Zeina Khodr, who is reporting from Gweir, near the frontline.

Fighting was ongoing late in the day.