An 18th-century Chinese jade imperial seal sold for €1.68 million ($2.2 million) at a Paris auction house this week, despite protests from Chinese officials that the relic was stolen by British and French troops from the Imperial Summer Palace in 1860, BBC News reports.

The Qing Dynasty relic, a seal mounted with two carved dragons, sold for five times its pre-sale estimate after a bidding war between two hopeful buyers. The winner, a Chinese bidder, would not give his name but said he was acting on behalf of an art collector in France.

The Chinese government said the seal is loot taken at the end of the Second Opium War and should be returned. "We once again express strong indignation at this sort of repeated action that hurts the Chinese people's feelings, harms their cultural interests, and violates international pacts."

The auction house received the seal from the heirs of a French general, Elie Jean de Vassoigne, who commanded invading forces, according to Xinhua news agency.

The sale comes two months after China tried to block the Christie's sale of two Qing Dynasty bronze animal heads taken from the same palace. A Chinese buyer bought those pieces, a rabbit and a rat head, for €15 million each but then announced that he would not pay. The Chinese government said it had no connection with the bidder.