Unrecognisable: Fans concerned by frail-looking Liam Neeson

Fans are concerned for Liam Neeson's health after he was photographed in New York this weekend. Photo / Getty

Fans have expressed concern about popular action star Liam Neeson after he was photographed looking gaunt in New York City in the weekend.

The 63-year-old was barely recognisable as he strolled around the city on Saturday, sporting a baseball cap and sunglasses.

A spokesperson told the Daily Mail there is no cause for concern and "he has never been healthier".

Neeson as tough guy Bryan Mills in Taken, the action thriller that revived his career. Photo / 20th Century Fox

Gossip website Radar reported the star has cleared his schedule, adding fuel to speculation that all is not well. However, his spokesperson says he is due to start work on a new film in September after finishing another project.

The actor recently told the Daily Mail's Sebastian Shakespeare that growing older was a "touchy subject".

"My birthday is a touchy subject. I'm going to be 63 - nobody wants to be 63. I'm getting old.

"What I want more than anything is for it to be ignored. I just hate it and it makes me feel vulnerable. It's such a private thing - the day you were born, the day you came out of your mother's womb.

"Some people hire a boat and do grand things like that, but I just get embarrassed about that sort of celebration and attention."

Fans took to Twitter to express their concerns for the popular actor, describing him as "pale, frail and unrecognisable".

Oh I can barely believe this is Liam Neeson. I hope he's ok. #liamneeson https://t.co/NcsRQag4k2

— Shannon the Irish (@ShannonBullins1) July 27, 2015

- nzherald.co.nz