An unprecedented collection of paintings by 20th century abstract master Nicolas de Stael have been gathered for a show that opened in Paris on Friday -- including several even his own children have never seen. 

The exhibition at the Museum of Modern Art includes some 200 paintings by de Stael, a key figure in France's postwar art scene. 

They include several that have never shown in public because the prolific de Stael was hugely popular with private collectors from an early stage of his career. 

The collection has been pieced together from 65 private lenders spread across France, Switzerland, Britain, Belgium and the United States, curator Pierre Wat told AFP.

Around 15 have never been seen by de Stael's children, including masterpieces like "Flowers" from 1952 -- a period when US collectors in particular were snapping up his work. 

Born into an aristocratic family in Petrograd (now Saint Petersburg) in 1914, de Stael's parents fled the Russian Revolution, only for both to die in poverty and illness in Poland. 

Taken in by a Belgian industrialist, he trained in painting against the advice of his adoptive parents and travelled across France and North Africa as a young man, perfecting his skills.  

De Stael enlisted in the Foreign Legion in 1939 but was demobilized in 1940 and ended up in Paris where he became immersed in the abstract movement, particularly through a friendship with Georges Braque.

Most of his work was condensed into a dozen years up to his death by suicide in 1955, but was nonetheless marked by several radical changes in style. 

"He constantly changed his way of painting, evolving radically towards abstraction from 1942," said co-curator Charlotte Barat-Mabille.

The blocky, heavily textured and deceptively simple works quickly proved popular with buyers. 

Trips to the south of France and later Sicily helped shift him towards landscapes with bolder, sunnier colours that are among the highlights of the current exhibition. 

One stand-out is the huge canvas, "Parc des Princes" based on one of the first nighttime football matches in Paris, which sold for 20 million euros to a private collector a decade ago. 

Gustave de Staël was only one-year-old when his father killed himself. 

He says studying the work helped him come to terms with his father's decision. 

"I think he said everything he had to say, and then he left. He was a very happy and accomplished man as a result. You can't constantly require yourself to improve as you get older," he told AFP. 

Wat agrees that de Stael was someone "entirely dedicated to painting".

"His entire life was research, experimentation and the demand for absolute freedom," he said. 

Ever-conscious of his legacy, the painter destroyed countless works, especially from his earlier days. 

His son thinks there are around 1,100 paintings still in existence with roughly as many drawings. 

The exhibition runs at the Museum of Modern Art in Paris until January 21./ach 

ls/er/ach