LONDON (AFP).- The biggest exhibition of Matisse's paper cut-outs -- a technique the French artist invented in his final years -- is going on show in London, the Tate Modern gallery announced Friday.

"Henri Matisse: The Cut-Outs" brings together around 120 works made between 1943 and his death in 1954.

"Towards the end of his life, during the last decade, he found it extremely difficult to paint," said Tate director Nicholas Serota.

"From the early 40s and onwards, he began to pick up techniques he had experimented with on one or two occasions of taking pieces of coloured paper and cutting into that paper and making composition from these coloured sheets."

The exhibition, which opens in April next year, includes works from museums and private collections around the world. It will later visit New York.

"It is quite simply the most important exhibition of this phase of Matisse's work that has ever been staged and I think will ever be staged," said Serota.

"It has never been done before, in part because the works are fragile: they are in paper, they are in colour. The colours have proven astonishingly durable and they are amongst the most treasured works" in the museums that own the pieces, he said.

Among them is the collage "L'Escargot (The Snail)" (1953), which has not left London since it arrived in the 1960s, but which will go to New York.

The exhibition includes several of his emblematic "Nus bleus (Blue Nudes)" series.

The cut-outs were nothing like anything else that was being done at the time, said the exhibition's curator Nicholas Cullinan.

Pablo Picasso, who lived near Matisse in the south of France, was "stunned and more than jealous of his work", Cullinan said.

The Spanish artist was impressed because "this is an incredible thing for an artist at the end of their carrier to pull off, to invent not only a new style but essentially a whole new medium".

The exhibition runs in London from April 17 to September 7 2014, before transferring to the Museum of Modern Art in New York where it will run from October 14 to February 9, 2015.