Jackie Chan has reassured fans that his elderly appearance in recent photographs was for an upcoming film role.

The Hong Kong-born actor was photographed earlier this year with greying hair, sparking fans to speculate about his health.

The martial arts star addressed the speculation in a post on social media as he celebrated his 70th birthday with a series of pictures reflecting his illustrious career.

“Not so long ago, a lot of friends saw some recent photos of me on the internet, and they were all concerned about my health,” he wrote.

“I want to take this opportunity to let everyone know, don’t worry!

“It’s just a character appearance for my latest movie. The character requires me to have white hair, white beard and look old.

“Over the years, I’ve always been willing to try new things for a movie, no matter if it’s a challenging stunt or a breakthrough appearance for a character.”

The Honorary Oscar winner said he has been in the entertainment industry for 62 years but “I cherish every moment”.

“All I can say is: I love making movies and I love you all.”

The Karate Kid UK Gala Premiere – London
Jackie Chan (left) and Jaden Smith (right) arriving for the UK Gala Premiere of The Karate Kid (Yui Mok/PA)

Chan did not detail what role required him to look older, but he is set to reprise his role as Mr Han in the next Karate Kid instalment alongside Ralph Macchio, star of the 1984 original.

The actor spoke about turning 70, saying “every time I hear this number, my heart would stop for a second”.

He added: “I’m 70 years old already? After recovering from the shock, the second thing that would come to my mind is a saying that my big brother, Sammo Hung, once said: ‘Being able to grow old is a fortunate thing’.

“Especially for us stunt people, we don’t know how lucky we are to be able to grow old.”

Chan starred in more than 30 martial arts films in his native Hong Kong before achieving worldwide fame in Rumble In The Bronx in 1995.

He went on to star in a string of Hollywood films including the Rush Hour trilogy, Shanghai Noon and its sequel Shanghai Knights starring Owen Wilson, Around The World In 80 Days and the Kung Fu Panda franchise alongside Jack Black.