Foreign Secretary Boris Johnson has branded a terror attack on a Shiite Muslim cultural centre in the Afghan capital of Kabul as "despicable".
The atrocity left at least 41 people dead, and another 84 wounded.
The Islamic State-linked Aamaq news agency said three bombs were used in the assault, as well as a single suicide bomber who blew himself up inside the centre.
Scores of people had gathered at the complex to mark the 1979 invasion of Afghanistan by the former Soviet Union.
Mr Johnson said: "I am appalled by this despicable attack on a cultural centre in Kabul which has claimed so many innocent lives, and my heartfelt condolences go out to the victims and their families.
"We remain determined in our resolve to help the Afghan people overcome terror and we are committed to supporting the Afghan government in seeking a brighter future for its people."
The Foreign Secretary condemned the "hateful" ideology of Islamic State, which is also known as Daesh.
"Initial reports suggest that Daesh in Afghanistan have claimed responsibility. The disregard for humanity shown today bears all the hallmarks of their hateful ideology which must be countered wherever it is found.
"This is what the brave men and women of Afghanistan are committed to doing, with the help and support of their regional and international partners, the UK included."