The night started with the star sharing the best actress prize with Glenn Close at the Critics' Choice Awards.

But she wrote on Twitter: "Just after the show I learned that my dear angel of a horse, Arabella, is dying.

"I am rushing to her now to say goodbye."

The singer and actress added: "She is and was a beautiful horse. Our souls and spirits were one.

"When she was in pain, so was I. I will never forget the moments we shared. Long hikes together, galloping through the canyons. Feeding her cookies.

"She will forever be a part of me. I am very sad. But I wish for your pain to end, and the gates of heaven to open for you. I love you. Girl, where do you think you're goin?"

Earlier, she shared some warm moments with Close - one of her rivals for the Oscars - at the Critics' Choice ceremony in Los Angeles.

The best actress award was shared between Gaga for her role in A Star Is Born and Close for The Wife.

Gaga broke down in tears on stage, and also revealed that Close is "good friends" with her mum. She also won best song for Shallow.

Britain's Olivia Colman - the other main contender for best actress at the Oscars - won a separate prize for best actress in a comedy for period comedy-drama The Favourite.

Sandra Oh won best actress in a drama series for Killing Eve

The Critics' Choice winners are among the key indicators for who might triumph at the Academy Awards on 24 February. Christian Bale won both best actor and best actor in a comedy for Vice.

Roma, Alfonso Cuaron's black-and-white portrait of the life of a maid in Mexico City in the early 1970s, was named best film.

The ceremony also honours TV shows, and the other British winners included Matthew Rhys, Ben Whishaw and Thandie Newton.

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All the Critics' Choice winners:

• Best picture - Roma
• Best actress - Glenn Close (The Wife) and Lady Gaga (A Star Is Born)
• Best actor - Christian Bale (Vice)
• Best actress in a comedy - Olivia Colman (The Favourite)
• Best actor in a comedy - Christian Bale (Vice)
• Best supporting actor in a film - Mahershala Ali (Green Book)
• Best supporting actress in a film - Regina King (If Beale Street Could Talk)
• Best young actor/actress - Elsie Fisher (Eighth Grade)
• Best acting ensemble - The Favourite
• Best sci-fi/horror movie - A Quiet Place
• Best action movie - Mission: Impossible - Fallout
• Best comedy - Crazy Rich Asians
• Best foreign-language film - Roma
• Best animated feature - Spider-Man: Into the Spider-Verse
• Best director - Alfonso Cuaron (Roma)
• Best score - Justin Hurwitz (First Man)
• Best song - Shallow (A Star Is Born)
• Best visual effects - Black Panther
• Best cinematography - Alfonso Cuaron (Roma)
• Best adapted screenplay - Barry Jenkins (If Beale Street Could Talk)
• Best original screenplay - Paul Schrader (First Reformed)
• Best drama series - The Americans
• Best actress in a drama series - Sandra Oh (Killing Eve)
• Best actor in a drama series - Matthew Rhys (The Americans)
• Best supporting actress in a drama series - Thandie Newton (Westworld)
• Best supporting actor in a drama series - Noah Emmerich (The Americans)
• Best comedy series - The Marvelous Mrs Maisel
• Best actress in a comedy series - Rachel Brosnahan (The Marvelous Mrs Maisel)
• Best actor in a comedy series - Bill Hader (Barry)
• Best supporting actress in a comedy series - Alex Borstein (The Marvelous Mrs Maisel)
• Best supporting actor in a comedy series - Henry Winkler (Barry)
• Best actress in a TV movie or limited series - Amy Adams (Sharp Objects) and Patricia Arquette (Escape At Dannemora)
• Best actor in a TV movie or limited series - Darren Criss (The Assassination of Gianni Versace: American Crime Story)
• Best supporting actor in a TV movie or limited series - Ben Whishaw (A Very English Scandal)
• Best supporting actress in a TV movie or limited series - Patricia Clarkson (Sharp Objects)
• Best movie made for TV - Jesus Christ Superstar Live in Concert