A man has died following what is believed to be a domestic violence-related stabbing in the Perth suburb of Joondalup.
Police said they were called to a disturbance on Plaistow Street just before 9pm on Thursday, where they found the man in his 30s suffering serious stab wounds.
"On arrival, officers located a man believed to be in his 30s with serious injuries," WA Police said in a statement.
"St John Ambulance WA personnel attended but the man was unable to be revived.
"A woman in her 20s is currently assisting Homicide Squad detectives with their inquiries.
"It is believed the man and woman are known to each other."
Just under four hours later, a separate suspected domestic violence incident in the suburb of Willagee left a woman in her 30s requiring hospital treatment for serious injuries.
After finding the woman, officers used a police dog to track down a man nearby.
"The 33-year-old man was taken into custody and is assisting police with their investigation," WA Police said.
"The man and woman are known to each other."
Anyone with information about either incident has been urged to contact police.
National Domestic Violence Service: 1800 RESPECT (1800 737 732). If you are in immediate danger call triple zero (000).