Gregory Itzin has died at the age of 74, his friend and 24 director and producer Jon Cassar has confirmed.
Writing on Twitter today (Friday 8th July), Cassar said: "My friend Greg Itzin passed away today. He was one of the most talented actors I had the honor to work with, but more than that he was an all around great guy.
"He'll be missed by his 24 family who had nothing but love & respect for him.
"You made your mark, now rest in peace friend."
Itzin joined the cast of hit action series 24 in its fourth season, playing Vice President Charles Logan, a role which went on to earn him two Emmy nominations.
In season 5, with Logan becoming President, he became one of the central characters opposite Kiefer Sutherland's Jack Bauer.
Logan is remembered as one of the greatest antagonists of the series.
In addition to 24, Itzin is known for appearances in Star Trek, playing five different roles over the years in Star Trek: Enterprise, Star Trek: Voyager and Star Trek: Deep Space Nine.
He also played the father of Paul Rudd's Mike Hannigan in Friends and had a number of stage acting credits to his name.
These included a turn in Pulitzer Prize-winning The Kentucky Cycle, for which he earned a Tony Award nomination.
Tributes have poured in on social media, with one fan writing: "Greg Itzin was outstanding in 24 (and in other roles of course). Seldom have I hated a character more and seldom have I enjoyed hating a character more. Thank you Mr. President."
Another called him and "amazing actor", adding that he was "the best character on 24 as Charles Logan".
"Rest in peace Gregory Itzin," a third tweeted. "I'll NEVER forget you on 24.. one of the best played characters ever, we will miss you President Logan."