Karratha man suffers face and arm lacerations after alleged attack while sleeping on couch

Police would like to speak with anyone who was near the intersection of Withnell Way and Searipple Road on Sunday morning. (ABC Pilbara: Amelia Searson)

A 24-year-old man is "lucky to be alive" after he was allegedly attacked with a machete or a similar edged weapon in Western Australia's north.

Police allege an 18-year-old man assaulted the victim while he was sleeping on his couch with another person after a house party in Karratha on Sunday morning.

Officer-in-charge of Karratha detectives Jason Blaine said the 18-year-old had been charged with grievous bodily harm.

He alleged the "suspect … used what we believe is a machete or an edged weapon to strike the owner of that house, who was asleep on the couch, across the face and the head a number of times".

Detective Senior Sergeant Blaine said the victim was flown to Royal Perth Hospital for treatment.

"He's very, very lucky to be alive, we would suggest," he said.

"He has a number of gash wounds to his head and also his arm, where he's tried to protect himself."

Jason Blaine says the victim has suffered serious injuries to his face and arm. (ABC News: Amelia Searson)

Police seek information

Police say the pair are believed to have known each other.

Senior Sergeant Blaine said detectives were appealing for information from those who were at the house party and anyone who was near the intersection of Withnell Way and Searipple Road between 3am and 6am on Sunday.

"We're aware there were 10 to 12 people at that house — we've spoken to a couple of those people," he said.

"We're pretty keen to speak to everyone that was there to find out what was going on, try to find a motive for what occurred."

An 18-year-old Karratha man has been charged with grievous bodily harm over the alleged assault. (ABC Pilbara: Amelia Searson)

Weapon missing

Senior Sergeant Blaine said police were also searching for the weapon used in the incident.

"We haven't found the weapon at this stage and we're appealing to the public to give us a hand if it's been discarded somewhere between Bulgarra and where [the alleged attacker] ran to, which we know is Cattrall Park," he said.

Senior Sergeant Blaine said the alleged assault was likely an "isolated incident" and the general public did not have to be concerned.

"There's a reason for [the alleged assault] — we just don't know what that is.

"So we don't have any concerns that someone is running around just randomly doing this.

"The person that we alleged committed the offence was there, he was there with the victim, he knows the victim and we obviously think there's some history that would lead to that."