The entertainment world is in shock at the news of the death of James Gandolfini, the American actor best known for his role as the mob boss in The Sopranos.

Gandolfini, 51, died after a heart attack while on holiday in Rome where he was due to attend the 59th Taormina Film Festival.

He was best known for his portrayal as Tony Soprano, described by critics as one of the best-loved TV characters of the early 21st century.

"Our hearts are shattered and we will miss him deeply," his managers said. "He and his family were part of our family for many years and we are all grieving."

ITV News Correspondent Robert Moore reports:

In a statement HBO called him a "special man, a great talent, but more importantly a gentle and loving person who treated everyone, no matter their title or position, with equal respect".

Gandolfini played Tony Soprano in the groundbreaking series that aired from 1999 to 2007, winning three Emmy awards and a Golden Globe for his portrayal of the conflicted mob boss who was both brutal and emotionally delicate.

Sopranos creator David Chase described Gandolfini as "a genius", saying: "Anyone who saw him even in the smallest of his performances knows that.

"He is one of the greatest actors of this or any time. A great deal of that genius resided in those sad eyes."

British comedy writer and producer Armando Iannucci, who directed James Gandolfini in the 2009 film In The Loop, paid tribute to the actor:

Claudio Modini, director of emergency room at the Polyclinic Umberto I hospital, said Gandolfini arrived in cardiac arrest and doctors tried for 40 minutes to restart the actor's heart before he died at 11pm local time.

Twitter was dominated with tributes to Gandolfini as actors, comedians, writers and public figures discovered the news.

Comic actor Robin Williams:

Back to the Future actor Michael J Fox:

Former Downing Street communications chief Alastair Campbell:

Comedy writer Simon Blackwell worked with Gandolfini on In The Loop:

Labour MP Chris Bryant:

British actor Paddy Considine:

Comedian Ricky Gervais:

British actor Ewan McGregor: