The US consulate in the south-western Chinese city of Chengdu has officially closed amid simmering tensions between the two nations.

The US State Department said the consulate officially suspended operations at 10am on Monday (local time).

Chinese state broadcaster CCTV confirmed the US flag had been lowered.

The closure drew crowds of locals, who yelled out patriotic slogans from the front of the consulate while the flag was lowered. Surrounding streets were also blocked by a huge police and security presence, cutting off virtually any view of the property.

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Beijing had ordered the consulate to shut in retaliation for a US order to shut down the Chinese consulate in Houston last week.

Earlier, the State Department expressed disappointment at China’s decision and said the US would try to continue its outreach to the region through its other missions in China.

The consulate had “stood at the centre of our relations with the people in Western China, including Tibet, for 35 years”, it said.

The tit-for-tat closings have marked a significant escalation in the tensions between the US and China on a range of issues, including trade, technology, security and human rights.

Moving trucks arrived at the US consulate on Sunday afternoon and left a few hours later.

Late at night, flatbed trailers entered the complex. One later emerged carrying a large shipping container and a crane.

Even before the closure, there was a steady stream of onlookers at the consulate over the weekend as Chengdu, like Houston, found itself in the limelight of international politics.

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People stopped to take selfies and photos, jamming a footpath busy with shoppers and families with strollers on a sunny day.

A little boy posed with a small Chinese flag before plainclothes police shooed him away as foreign media cameras zoomed in.

Uniformed and plainclothes officers kept watch on both sides of barriers after scattered incidents following the Chengdu announcement on Friday, including a man who set off firecrackers and hecklers who cursed at foreign media shooting video and photos of the scene.

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One man was quickly taken away after trying to unfurl a large placard late Sunday that he called an open letter to the Chinese government.

The US has alleged that the Houston consulate was a nest of Chinese spies who tried to steal data from facilities in Texas, including the Texas A&M medical system and the University of Texas MD Anderson Cancer Centre in Houston.

China said the allegations were “malicious slander.”

-AAP