Image copyright AP Image caption Al Molinaro starred as 'Big Al' alongside Henry Winkler, as the Fonz

Al Molinaro, who starred as "Big Al" Delvecchio in US sitcom Happy Days, has died at the age of 96.

He died in a California hospital of complications from a gallstone infection, his son Michael said.

The actor appeared as the owner of Arnold's Drive-in in the show, where the main characters would gather, from 1976 until 1982.

Henry Winkler, who appeared as The Fonz, led tributes saying Molinaro was "a gentle soul".

"Very thoughtful and funny. He will be greatly missed," Winkler wrote on Twitter.

Image copyright AP Image caption The Fonz, played by Henry Winkler (c), and Richie Cunningham, played by Ron Howard (l), would gather at the drive-in in the 1950s-set sitcom

Molinaro had taken over the role of Al two years into the series' run and starred in more than 100 episodes.

The part had originally been played by Pat Morita, who went on to star as Mr Miyagi in Karate Kid.

Molinaro told the LA Times: "When you live with a character as long as I have, you know how he would talk in almost any situation."

The Wisconsin-born actor also appeared in Happy Days spin-off series Joanie loves Chachi in the 1980s.

Scott Baio - who played Chachi Arcola in both Happy Days and the spin-off show - also paid tribute, tweeting a picture of them together and saying: "Al, the sweetest man I ever knew. I will miss you."

Image copyright Twitter

Molinaro, who also spent five years playing Murray the cop in the TV version of The Odd Couple, retired from acting in the 1990s.

After retirement, he became best known for commercials and set up a chain of diners called Big Al's. He also reprised the character of Al in the music video for Weezer's song, Buddy Holly.

The band tweeted: "RIP Al Molinaro. Loved having you in the Buddy Holly video."

Image copyright Twitter

Speaking in 1992 on a Happy Days reunion show, Molinaro described the 1950s-set sitcom as an "important" show.

"In the industry, they used to consider us like a bubble-gum show," he said.

"But I think they overlooked one thing. To the public in America, Happy Days was an important show, and I think it was and I think it still is."