ACT Policing is seeking witnesses or information about four incidents in Calwell on Tuesday and Saturday.

About 5pm on Tuesday, a stranger asked a man a question before allegedly lunging at him with a knife.

Half an hour later, a woman was walking near an underpass beneath Johnson Drive when a person carrying a knife approached and she ran away.

At 7.30pm, a man was approached near Beazley Cres, Calwell. The stranger lunged at him with a knife and he suffered a stab wound in the back. He was taken to Canberra Hospital in a stable condition.

About 9.40pm on Saturday, someone approached another man, demanding his phone. The person allegedly attacked the man with a knife and ran off.

Police believe these incidents are linked and likely to have been the actions of one person.

As the incidents all occurred at night, descriptions of the wanted man have varied. The consistent information is that the man is in his 20s or 30s and has dark hair.

Residents in the Calwell area are urged to be aware of their surroundings when out walking and to report any suspicious activity immediately to police on 131 444.

Anyone with information about these incidents, including CCTV that captures the man, should call Crimestoppers on 1800 333 000 or online quoting reference number 6550531. Information can be provided anonymously.