The band, who have been on hiatus since mid-2009, have appeared together in a festive snap posted on their official Twitter page, Twitter.com/thisisblocparty.
Frontman Kele Okereke, bassist Gordon Moakes, guitarist Russell Lissack and drummer Matt Tong all appear in the picture, which is captioned: "Merry Christmas from the Bloc".
Earlier this year, Okereke released his debut solo album 'The Boxer' - and at the time told NME he was unsure whether Bloc Party would ever get back together.
"Who knows how we'll feel about anything in a year's time?" he said.
Moakes and Lissack have also worked on side projects - the former as part of hardcore band Young Legionnaire and the latter in Anglo-American duo Pin Me Down.
Lissack has also worked as Ash's touring guitarist since Bloc Party went on hiatus.
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