The American flag was lowered at the US consulate in Chengdu yesterday and Chinese authorities took charge of  the building, as Beijing carried out a Cold War-style retaliatory closure of the mission.

Relations have deteriorated in recent weeks in an intensifying standoff between Washington and Beijing, with the Chengdu mission ordered to shut in retaliation for the forced closure of the Chinese consulate in Houston, Texas.

Beijing confirmed that the consulate had closed at 10:00am. "Afterwards, Chinese authorities entered through the front entrance and took it over," the foreign ministry said in a statement.

Both consulates closed 72 hours after the respective orders were made.

A State Department spokesman told AFP the mission's diplomats and their dependents would leave China by August 27.

Video footage published later yesterday by the US embassy on Chinese social media platform Weibo showed US Marines in dress uniform lowering and folding the Stars and Stripes from the front of the consulate, before handing it to consul general Jim Mullinax.

Both US and China have alleged that the respective consulates were engaged in activities against national security.

"Today, we bid farewell to the US consulate in Chengdu. We will miss you forever," the US embassy in Beijing posted on Weibo.

In a separate statement the consul general posted that his mission had provided services to more than 200 million people in southwest China and Tibet, and had given "thousands" of visas every day to Chinese students and tourists.

The Chengdu consulate covered southwest China, including Tibet. Many Tibetans accuse the central government of religious repression and eroding their culture.

Tensions have soared between the world's two biggest economic powers on a range of fronts including trade, China's handling of the novel coronavirus and a tough new security law imposed on Hong Kong, with US officials warning of a "new tyranny" from China.

Nationalistic tabloid the Global Times warned in an editorial Monday that if Washington was "determined to push China-US ties in the worst direction... the 21st century will be darker and even more explosive than the Cold War era".

It said the rising tensions could lead to "unprecedented catastrophe".