A video showing renovation work at Egypt's Menkaure pyramid at Giza has triggered social media criticism, with one expert decrying its "absurdity".
Mostafa Waziri, the head of Egypt's Supreme Council of Antiquities, has in contrast dubbed it "the project of the century."
In a video posted on Facebook on Friday, Waziri showed workers setting blocks of granite on the base of the pyramid, which sits besides the sphinx and the larger Khafre and Cheops pyramids at Giza.
When originally built, the pyramid was encased in granite, but over time lost part of its covering. The renovation aims to restore the structure's original style by reconstructing the granite layer.
Work is slated to last three years and will be "Egypt's gift to the world in the 21st century", said Waziri, who heads the Egyptian-Japanese mission in charge of the project.
But under the video, dozens of upset people left comments critical of the work.
"Impossible!" wrote the Egyptologist Monica Hanna.
"The only thing missing was to add tiling to the pyramid of Menkaure! When are we going to stop the absurdity in the management of Egyptian heritage?" she asked.
"All international principles on renovations prohibit such interventions, Hanna added, calling on all archaeologists to "mobilise immediately."
Other commentators reacted with sarcasm.
"When will the project to straighten the Tower of Pisa be planned?" asked one.
"Rather than tiles, why not wallpaper the pyramids?" said another.
The issue of heritage preservation in Egypt -- which derives 10 percent of its gross domestic product from tourism -- is often the subject of heated debate.
Recent destruction of entire areas of Cairo's historic area led to powerful mobilisations by civil society, which is largely banned from political activity and now concentrates the bulk of its fight with the government on urban planning and heritage issues.
The debate has lately focused on the fifteenth-century Abu al-Abbas al-Mursi mosque in the coastal city of Alexandria, Egypt's second largest.
Local authorities announced an investigation after a contractor in charge of renovation decided to repaint in white the ornate, carved and coloured ceilings of the city's largest mosque.
