Three hundred Iraqi soldiers died in a chlorine gas attack carried out by the self-proclaimed Islamic State of Iraq and al-Sham (ISIS) in the Iraqi city of Fallujah, said Ali al-Budairi, an Iraqi MP from the Shia-dominated National Iraqi alliance in the Iraqi Parliament on Monday.

It is unclear when the attacks took place. ISIS's use of chlorine gas in attacks isn't new. There are reports that the ISIS militants used chlorine-war gas before.

Speaking at a press conference in the Iraqi Parliament on Monday, Ali al-Budairi said: "ISIS killed 300 out of 400 soldiers they besieged in Saqlawiya district of northern Fallujah, using chlorine gas."

Al-Budairi held Anbar's operations chief Rashid Falih and new Iraqi Prime Minister Haider al-Abadi responsible for failing to immediately send army backup to the district.

ISIS, which already controls parts of Syria, has extended its reach into Iraq since June 10.

Violence conducted by the ISIS militants has claimed more than 1,400 lives in Iraq, and caused 1.2 million Iraqis, including Turkmens, Arabs, Christians and Ezidis, to flee their homes.