On Monday, Chinese residents took to social media to express their displeasure with billionaire Tesla creator Elon Musk’s space ambitions after China protested that its space station had to take evasive steps to avoid colliding with satellites launched by Musk’s Starlink program.

According to a statement provided by China earlier this month to the United Nations’ space agency, satellites from Starlink Internet Services, a part of Musk’s SpaceX aerospace business, made two “close encounters” with the Chinese space station on July 1 and Oct. 21.

“The China Space Station deployed preemptive collision avoidance control for safety considerations,” China said in a document posted on the UN Office for Outer Space Affairs’ website.

The complaints have not been independently verified. SpaceX did not immediately respond to a request for comment.

In a post on China’s Twitter-like Weibo microblogging platform on Monday, one user said Starlink’s satellites were “just a pile of space junk”, while another described them as “American space warfare weapons”.

With nearly 30,000 satellites and other debris believed to be orbiting the planet, scientists have urged governments to share data to reduce the risk of catastrophic space collisions.

SpaceX alone has deployed nearly 1,900 satellites to serve its Starlink broadband network, and is planning more.

“The risks of Starlink are being gradually exposed, the whole human race will pay for their business activities,” a user posting under the name Chen Haiying said on Weibo.

U.S. space agency NASA was forced to abruptly call off a spacewalk at the end of November, citing risks posed by space debris. Musk tweeted in response that some Starlink satellite orbits had been adjusted to reduce the possibility of collisions.

China began constructing the space station in April with the launch of Tianhe, the largest of its three modules. The station is expected to be completed by the end of 2022 after four crewed missions.

Musk has become a well-known figure in China, though Tesla’s electric-vehicle business has come under growing scrutiny from regulators, especially after a customer climbed on top of a Tesla car at the Shanghai auto show in April to protest against poor customer service.