The Pentagon formally complained to the Chinese government on Thursday, accusing Chinese nationals of pointing lasers at US military aircraft near Djibouti, in east Africa, multiple times in the past few weeks.
"They are very serious incidents," Dana White, a Pentagon spokeswoman, told reporters, adding: "We have formally démarched the Chinese government, and we've requested the Chinese investigate these incidents."
The Chinese Defense Ministry, which has a military base just miles from the US's Camp Lemonnier in Djibouti, denied the accusations.
China's naval base in Djibouti, which opened last year, is Beijing's first overseas military base.
Citing military officials, The Wall Street Journal reported Thursday that in past weeks, there had been at least four incidents in which US service members have been targeted with military-grade or non-military-grade lasers originating near a Chinese military installation in Djibouti. There have also been additional incidents occurring within US Pacific Command, the officials said.
Since 2015, China has had at least four kinds of blinding laser weapons: the BBQ-905 Laser Dazzler Weapon, the WJG-2002 Laser Gun, the PY132A Blinding Laser Weapon, and the PY131A Blinding Laser Weapon.
The four weapons "look like oversized assault rifles or shoulder-fired grenade launchers," according to The War Zone. They could possibly violate the United Nations Protocol on Blinding Laser Weapons that Beijing signed in 1998, The Washington Free Beacon reported.
In a recent incident, two C-130 pilots became dizzy and saw "rings," a Pentagon official told The Journal, adding that they are recovering.
"These incidents are not surprising as they represent an act just short of war, but indicate gross, intentional negligence, as well as complete disregard for aviation safety and international norms," Trey Meeks, a principal at the Asia Group research firm, told The Journal. "I would certainly view it as harassment."
US pilots have begun wearing eye protection or visors for protection and are even planning their flights around Chinese military flights, The Journal reported.
The US military has issued a Notice to Airmen about "multiple lazing events involving a high power laser" in Djibouti, saying to "use extreme caution when transiting near this area," according to The Diplomat. The Federal Aviation Administration also sent the notice in April.
The incidents come at a contentious time in US-China relations. US President Donald Trump has announced tariffs on Chinese goods and restrictions on certain US technology exports.
China and Russia have also recently forged a military partnership, which China's defence minister said would "let the Americans know about the close ties between the armed forces of China and Russia.