Previously unpublished letters written by artist Rene Magritte are set to go under the hammer with an antiques valuation of between $150,000 (£93,113) and $250,000.

The documents - which come complete with around 40 drawings - will be sold at Sotheby's in New York, the Guardian reports.

According to the auction house, the items are rare and they suggest the artist was as worried about how his paintings were marketed as the content of them.

Marsha Malinowski, Sotheby's book and manuscripts expert, said the pieces are extraordinary, adding: "Magritte letters are just very hard to find and to have them with so many drawings of his iconic images is extremely rare."

This comes after an antiques valuation of £120,000 was placed on a letter written by John Keats in 1820 to his neighbour Fanny Brawne, the publication revealed.

The item is set to go up for auction at Bonhams in March.

Unpublished Magritte letters to be sold with antiques valuation of $250k

A British art collector has had the surprise of a life-time when he had his drawing confirmed by various authentication boards, that his piece is indeed by Andy Warhol, and one of his first ever works produced. The signed sketch depicts Rudy Vally and was hidden among several works bought by Andy Fields, 48, during a trip to Las Vegas two years ago.

Andy Warhol Drawing Discovered could be worth $2 million

This remarkable early drawing by Raphael can be dated to circa 1503 at which time the young Raphel was collaborating with Pinturicchio on the fresco cycle in the Piccolomini Library, Siena.

Early drawing by Raphael to be sold in New York