Sydney police have appealed for the return of an 85-year-old whom they believe was kidnapped by mistake.

Chris Baghsarian, who lived alone, was taken from his house in the suburb of North Ryde by at least three attackers early on Friday morning, and bundled into a dark-coloured SUV.

"They were intending to take somebody, but have taken the wrong person," Det Acting Supt Andrew Marks told reporters on Monday, adding that no ransom note had been received.

"The family are in distress. All they want is their father to be returned, their grandfather to be returned," he said, appealing for people to report any unusual activity seen around properties known to be empty.

The appeal came as the Sydney Morning Herald (SMH) reported that videos and images of a severely injured Baghsarian in an unknown location were circulating in Sydney's underworld.