Australian police said Friday they were treating the murder of an elderly couple in their Brisbane home as a terrorism incident.

Police linked the murders to Raghe Mohamed Abdi, who had previously been investigated by counter-terrorism police, after he was shot dead in a confrontation with officers on a Brisbane highway Thursday morning.

The 22-year-old was shot after he threatened officers with a knife, police said.

That afternoon, police said they were called to a nearby address for a welfare check and discovered the bodies of an 87-year-old man and 86-year-old woman.

"Further examination of both that scene, and the scene of the police shooting yesterday, has uncovered for us what we believe to be a direct link between the two matters," Queensland Police Deputy Commissioner Tracy Linford said in a press conference Friday.

An item allegedly discovered on Abdi was believed to be taken from the deceased couple's home, while several items at the home were linked to the man, Linford added.

Police in Australia have said they are treating the murder of an elderly couple in Brisbane as a terrorism incident
Police in Australia have said they are treating the murder of an elderly couple in Brisbane as a terrorism incident AFP / PATRICK HAMILTON

The combination of the Abdi's past, his alleged attempt to harm police and the link to the murder scene made it "pretty clear that we need to treat this as a terrorism event", she said.

The exact motivation of the killings remain unclear, Linford added.

Abdi had previously been detained after attempting to fly to Somalia in 2019 -- where police alleged he aimed to join a terrorist organisation -- and had removed a tracking device before Thursday's incident.

But his lawyer, speaking before the link to the murder investigation was made public, told national broadcaster ABC that the police were incorrect to connect him with terrorism and labelled yesterday's shooting as a "significant adverse mental health event".

"When he was going to Somalia to visit relatives, he was held for 18 hours and investigated as to whether he was going to Somalia as a foreign fighter," Terry O'Gorman said.

"There was no evidence to justify holding him and 18 months later, he has never been charged with that offence."

Abdi was never charged with terrorism offences and was instead on bail for other charges, police said.