A 3,000-year-old stone bust of Tutankhamun, set to be auctioned on July 4. (AFP)

Egypt on Wednesday condemned a planned London auction by Christie's of a head from a statue of Pharoah Tutankhamun, which is set to proceed despite Cairo's concerns over paperwork.

Egypt's ambassador to the UK "regrets that the auction house intends to conduct a new sale involving Egyptian artefacts tomorrow (Thursday), including the head of Tutankhamun, without the backing of papers", said a joint statement by its foreign and antiquities ministries late Wednesday.

"The auction house still has not furnished the papers with Egyptian authorities", the statement added.

Christie's expects the 28.5-centimetre (11-inch) brown quartzite relic from the Valley of the Kings to fetch more than 4 million pounds ($5.1 million, 4.5 million euros).

The Egyptian statement said auctions of other ancient Egyptian items had taken place earlier on Wednesday, despite "legitimate Egyptian requests in recent weeks" centring on sales certificates.

The sales are "in contradiction with international agreements and conventions", the statement said.

The pharoah's finely-chiselled head -- its serene eyes and puffed lips emoting a sense of eternal peace -- comes from the private Resandro Collection of ancient art that Christie's last sold in 2016 for £3 million.

"We would not offer for sale any object where there was concern over ownership or export," Christie's said in a recent statement released to AFP, noting that the Egyptian embassy had been notified in advance of the planned sale.

The French-owned British auction house explained that the current lot was acquired by Resandro from a Munich-based dealer in 1985.

It traces its prior origins to the 1973-74 acquisition by another dealer in Austria from the Princely House of Thurn and Taxis in modern-day Germany.

But little is known to the public about how the statue found its way to Europe.