Two people have been struck by a car and killed on a major highway not long after parking their own vehicle in an emergency lane and getting out.

The 31-year-old woman and a man aged 24, not 21 as previously reported by police, suffered critical injuries and died at the scene on Forrest Hwy in South Yunderup, near Mandurah south of Perth.

WATCH THE VIDEO ABOVE: Two people killed on the Forrest Highway.

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The pair had stopped their white MG sedan in the southbound emergency lane just south of Pinjarra Rd about 6.20pm on Sunday.

“A short time later, a dark blue Volvo wagon travelling south ... collided with the pedestrians on the highway,” WA Police said.

“The driver of the Volvo stopped at the scene, called emergency services and rendered assistance.”

7NEWS understands the pair were travelling to Waroona to drop off Mother’s Day presents when they were hit.

Major Crash is investigating and has appealed for information.

Anyone with details should contact Crime Stoppers.