A Sydney family is mourning a father-of-two who was killed while cycling through a cemetery in the city's south.

Ron Doolan, 39, was struck by a Toyota Corolla while riding though Sutherland's Woronara Cemetery just before 7am today.

Mr Doolan became trapped under the car and died at the scene.

Ron Doolan died at the scene. (Supplied)

It is believed the car and bike were travelling in the same direction at low speed and police are treating the the crash as a freak accident.

There is a 20km/h speed limit in the cemetery and witnesses have told police the driver was abiding by those rules.

"It's awful, 23 years in the job and I've never seen an incident like this," Chief Inspector Chris Hill from NSW Police said.

Woronora Cemetery. (Google Maps/ File Image)

The accident occurred about 7am. (Google Maps)

Woronora Cemetery CEO Graeme Boyd said staff were shocked.

"This is extremely traumatic, it doesn't make sense as to how it's occurred," Mr Boyd said.

"We're from the community for the community in this cemetery, everything is geared around that, it's all low speed, how this has occurred, no one knows."