In 2023Mar, 20th anniversary of the invasion of Iraq led by the US & the UK and the 1st anniversary of the invasion of Ukraine by Russia, the AFP News Agency posted an interview with former UK Prime Minister, Tony Blair: Tony Blair: Putin can't use Iraq invasion as justification for Ukraine | AFP.
Blair stated:
The idea that removing a dictator [Saddam Hussein] who's brutalised his people, engaged in two regional wars, in breach of [multiple] UN resolutions and killed 12,000 people in one day through the use of chemical weapons [...]
When did Saddam Hussein kill 12,000 people in one day with chemical weapons?
The closest I found is Halabja massacre, but 3,200 - 5,000 people died on that day, not 12,000.