A Townsville teenager is in a critical but stable condition in hospital after he was stabbed in the neck with a sword.

The 18-year-old was found by neighbours on Thursday morning after he left a unit on Cook St in North Ward and walked down the street.

Detective Sergeant Brenden Stevenson said two swords were located at the property, but police didn't believe his attacker followed him down the street.

Det Sgt Stevenson said initial investigations showed the young man was stabbed with a sword "in the neck region".

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He praised neighbours for their help and said the teenager could have died without their assistance.

Det Sgt Stevenson said another 18-year-old man, believed to be the victim's flatmate, had been taken into custody and was assisting police with their inquiries.