Thousands are queuing at Copenhagen Zoo to see two giant black-and-white bears on loan from China under Beijing's popular "panda diplomacy" initiative.

Denmark's Australian-born Crown Princess Mary untied a red velvet ribbon to open the gates Thursday in her capacity as the zoo's patron. She was assisted by her twins, Princess Josephine and Prince Vincent.

The opening came a day after Mary's mother-in-law Queen Margrethe inaugurated the Panda House that's been built for 6-year-old male Xing Er, and Mao Sun, a 5-year-old female.

The bears arrived last week in cargo containers and were driven to the zoo's new 160-million kroner ($24.2 million) yin-yang shaped enclosure.

Beijing has lent out pandas as a sign of goodwill. Any cubs born during the 15-year loan period are considered China's.