The item depicting the boy king as the god Amen was alleged by Egyptian experts to have been stolen from its homeland.

British auction house Christie's defended its decision to press on with the sale of the ancient artefact, saying the statue had never been subject to previous investigations or allegations about its origins.

The price of the quartzite bust rose rapidly from a starting bid of STG3m ($A5.4m) to the STG4.7m ($A8.4m) it was sold for during the brief bidding process.

"This was a rare, beautiful and important work," a Christie's spokesman said.

"We recognise that historic objects can raise complex discussions about the past, yet our role today is to work to continue to provide a transparent, legitimate marketplace upholding the highest standards for the transfer of objects.

"There is an honourable market for ancient art and we believe it is in the public interest that works come out into the open with the opportunity for them to be researched, as well as seen and enjoyed by global audiences."

Former antiquities minister Zahi Hawass previously said the bust could have been taken from Karnak Temple during the 1970s.

Christie's firmly objected to the claims, and said it had gone through all necessary processes to be sure of its origins.

Australian Associated Press