18 people were admitted to hospital, with three in critical condition, after a man drove his car into a crowd of pedestrians in Melbourne yesterday.

One of those injured was a 25-year-old Irish citizen, a woman who is now in stable condition, the Independent.ie reports.

The three people in critical condition are a pair of South Korean men, aged 61 and 67, and an 87-year-old Melbourne native.

The youngest victim, a four-year-old boy from South Korea, is thankfully stable. Several others remain in hospital, including foreign nationals from India, China, and Venezuela.

The suspect, Saeed Noori, explained that some of his actions were motivated by the 'treatment of Muslims', police said.

The Independent.ie reports that despite this sentiment, police emphasise that there were no terrorist links found in their initial investigation.

Noori is a 32-year-old Australian citizen with a history of mental illness and drug abuse. He is currently in police custody.

The suspect, who is of Afghan heritage, was convicted of assault in 2010.

He is believed to have been receiving treatment for his mental health.

"Obviously we've done search warrants last night and we haven't found anything at all to indicate his linkage or involvement with any type of extremism, with any terrorist organisation or anything of a terrorist nature," said Victoria Police acting commissioner Shane Patton.

"So given the mental illness background and everything we need to step carefully and the investigation is ongoing."