Armed man hit by a car while evading police

A man seen with a knife in South Brisbane on Saturday evening suffered a "significant" head injury when he was hit by a car while allegedly evading police.

Queensland police are investigating the incident, which began when a man allegedly armed with a knife was seen acting "suspiciously" on Merivale Street before refusing police requests to stop.

A police statement said the man allegedly tried to enter a property before walking onto the road, where he was hit by a vehicle. Police gave him immediate assistance before paramedics were called at 5.35pm.

The man was taken to the Princess Alexandra Hospital in a serious condition with a "significant" head injury.

The Forensic Crash Unit is investigating.