A 3,000-year-old bust of Egyptian "Boy King" Tutankhamun has been auctioned for more than €5m in London despite an outcry from Cairo.

Christie's sold the 28.5cm quartzite head for €5,290,000 (£4,746,250) at one of its most controversial sales in years.

No information about the buyer has been disclosed.

The pharaoh's finely-chiselled face, its calm 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 €3.35m (£3m).

Egyptian officials had called for sale to be stopped and the treasure returned.

Egypt's foreign ministry said Christie's decision "contradicts international agreements and conventions."

Former antiquities minister Zahi Hawass said the piece appears to have been "stolen" in the 1970s from the Karnak Temple complex north of Luxor.

"We think it left Egypt after 1970 because in that time other artefacts were stolen from Karnak Temple," Mr Hawass said.

In response, Christie's said that Egypt had never before expressed the same level of concern about a bust whose existence has been "well known and exhibited publicly" for many years.

"The object is not, and has not been, the subject of an investigation," it said in a statement.

The auction house has published a chronology of how the relic changed hands between European art dealers over the past 50 years.

Its oldest attribution from 1973-74 places it in the collection of Prince Wilhelm of Thurn and Taxi in modern-day Germany.

Yet that account was called into doubt by a report from the Live Science news site last month suggesting the prince never owned the piece.

Prince Wilhelm was "not a very art-interested person," his niece Daria said.

A journalist and art historian who knew him told Live Science that the prince had no arts collection.

Tutankhamun is thought to have become a pharaoh at the age of nine and to have died about 10 years later.

His rule would have probably passed without notice were it not for the 1922 discovery by Britain's Howard Carter of his nearly intact tomb.

The lavish find revived interest in ancient Egypt and set the stage for subsequent battles over ownership of cultural masterpieces unearthed in colonial times.

Tutankhamun became commonly known as King Tut and made into the subject of songs and films.

International conventions and the British government's own guidance restrict the sale of works that were known to have been stolen or illegally dug up.

The British Museum has been wrangling for decades with Greece over its room full of marble Parthenon friezes and sculptures.

Egypt's own campaign to recover lost art gained momentum after numerous works went missing during the looting that accompanied former president Hosni Mubarak's fall from power in 2011.

Cairo has managed to regain hundreds of looted and stolen artefacts by working with both auction houses and international cultural groups.

But Egypt has been unable to substantiate its case with firm proof that the Tutankhamun bust was illegally obtained.

Christie's said that it would "not sell any work where there isn't clear title of ownership".