A "quietly explosive" film about a fracturing relationship has won the leading award at this year's Edinburgh International Film Festival, with one of its stars, Charlotte Rampling, also winning a prize.

The EIFF awards, for the 69th festival, have been announced ahead of the event's final weekend which closes on Sunday with the world premiere of Scott Graham's Scottish drama Iona.

The Michael Powell Award for Best British Feature Film was awarded to Andrew Haigh's 45 Years which received its UK Premiere at the festival.

The award was presented by actor Jane Seymour.

The winner was chosen by the Michael Powell Jury, chaired by LA Times film critic Kenneth Turan with actor/director Karen Gillan and actor Ian Hart.

The Michael Powell Jury said: "This year it goes to a quietly explosive film which represents classic filmmaking at its best.

"This is a measured yet provocative film, a masterclass in understated acting that was the unanimous choice of the jury."

Haigh, the director, said: "This is a real honour and made even more special when you consider the list of British films that have won before.

"All you can hope for when you make a film is that it resonates with people and that is why receiving an award such as this feels so fantastic."

The Award for Best Performance in a British Feature Film was shared between James Cosmo for his performance in The Pyramid Texts Texts and Charlotte Rampling for her performance in 45 Years.

The actor Ian Hart, a jury member, said: "There's an old actor's joke when someone's rehearsing a scene and they come across a certain piece of text and they say 'I don't need that line, I can do that with a look.'

"But most people can't so the line goes back in. But certain people can, they can do more with a gesture, they can do more with a look than most people can do with ten words, and this is why this award goes to Charlotte Rampling."

Karen Gillan said: "I think I speak to all up and coming Scottish actors when I say James Cosmo is a huge inspiration, his acting is a lesson to us all, you show us how it's done."

Charlotte Rampling, who could not attend the Filmhouse ceremony in person, said: "It is an extraordinary moment when you are singled out when the craft that you have been perfecting throughout your life is appreciated and rewarded.

"It is thrilling and humbling and I thank you so much for giving me the chance to feel so proud. I thank Andrew Haigh for seeing what he sees, Tom Courtenay for moving me to tears, and Tristan Golligher for believing that this could be made."

The Award for Best International Feature Film was awarded to Marielle Heller's The Diary of a Teenage Girl, which received its UK Premiere at EIFF.

The International Competition Jury said: "The Diary of a Teenage Girl is imaginative both visually and narratively, emotionally gripping and completely unapologetic in tone. We had a tough decision to make as we had some very strong contenders."

Ms Heller said: "Although this is an American film, it was made by a very international group, including our North Star, the British Bel Powley, whose brave performance is the heart of this film. I am so pleased to have such a prestigious UK premiere for the film at Edinburgh, and I am especially thrilled for Bel's performance to be brought to her home turf for the first time. And I am so honoured by this award, which was a wonderful shock."

The Award for Best Documentary Feature Film was awarded to Crystal Moselle's The Wolfpack.

Scrapbook directed by Mike Hoolboom won The Award for Best Short Film.

Voted for by the audience, The McLaren Award for Best New British Animation, supported by the British Council, went to Stems by director Ainslie Henderson.