American diplomatic staff have left their consulate in the Chinese city of Chengdu, after a 72-hour deadline expired.
China ordered the closure in response to the US closing the Chinese consulate in Houston, Texas, last week.
Before Monday’s deadline, staff were seen leaving the building, a plaque was removed, and a US flag was lowered.
China’s foreign ministry said Chinese staff entered the building after the deadline and “took over”.
A US State Department spokesperson said: “The consulate has stood at the centre of our relations with the people in Western China, including Tibet, for 35 years.
“We are disappointed by the Chinese Communist Party’s decision and will strive to continue our outreach to the people in this important region through our other posts in China.”
As the US consulate closed, crowds of local residents gathered outside, with many waving Chinese flags and taking selfies.
Beijing ordered the closure in response to the US closure of the Chinese consulate in Houston – over claims that it was used as a hub for spying.
Tensions have been escalating between the two countries over a number of issues:
What happened in Chengdu?
Chinese state media showed pictures of lorries leaving the US consulate, and workers removing diplomatic insignia from the building.
On Monday morning, state broadcaster CCTV posted a video online of the US flag being taken down.
Dozens of Chinese police were deployed outside the building, urging onlookers to move on.
However, boos were heard when a bus with tinted windows left the building on Sunday, the AFP news agency reports.
When Chinese diplomats left their mission in Houston last week they were jeered by protesters.