Washington has reportedly issued a formal complaint with China over what the US Federal Aviation Administration has described as “unauthorized laser activity,” which allegedly injured two US airmen.

According to reporting from Paul Mcleary at Breaking Defense, US officials are confident that China is responsible for the lasers, which they say are coming from the direction of a Chinese military installation in the African nation of Djibouti. The base in Djibouti is China’s first such overseas military facility and is situated near a US base.

“It’s enough that we’re concerned that we demarched them, and asked them to investigate. We’re confident,” Pentagon spokesperson Dana White told reporters on Thursday. She also said that about 10 laser-related incidents have taken place within the last several weeks.

“This sends a signal to Africa and globally that China has advanced weapons and is prepared to use them,” Dean Cheng, an expert on the Chinese military at the Heritage Foundation, told Mcleary. “The lack of an American response will be exploited as a warning that not even America dares stand up to China–so neither should you.”

Pentagon spokesperson Major Sheryll Klinkel said that in one recent incident two pilots landing a C-130 at the US base in Djibouti suffered minor injuries. Klinkel described the laser as “military grade.”

Mcleary noted that China is a signatory to the 1995 Protocol on Blinding Laser Weapons, under which the use of blinding weapons against humans is prohibited. China has denied allegations of Chinese involvement in the recent laser activity.

The development comes amid news that China has for the first time deployed missile systems to the Spratly Islands in the South China Sea, prompting a response from the White House.

“We’ve raised concerns directly with the Chinese about this,” White House press secretary Sarah Sanders said on Thursday regarding the missile deployment. “There will be near-term and long-term consequences,” she added.