Beijing, which operates a naval base in the Horn of Africa country, denied Pentagon accusations that Chinese personnel have targeted US pilots in the country with the beams, resulting in minor injuries to airmen and creating the potential for an accident.

"After careful verification, we have told the US explicitly that the so-called accusations are totally inconsistent with facts," foreign ministry spokeswoman Hua Chunying told reporters.

"You can remind relevant people in the US to pay attention to facts and not to make groundless accusations," she said during a regular briefing.

US officials issued a formal diplomatic complaint and demanded Beijing investigate a series of incidents dating back several weeks, Pentagon spokeswoman Dana White said Thursday.

"They are very serious incidents," White said.

"This activity poses a true threat to our airmen."

In one case, two pilots on a C-130 cargo plane suffered minor eye injuries as they came in to land at the base in the Horn of Africa nation, another spokeswoman, Major Sheryll Klinkel, told AFP.

Located at Djibouti international airport, the US military's Camp Lemonnier base is its only permanent facility in Africa. It is used largely for counter-terrorism operations in East Africa and Yemen.

China last year opened a naval base in Djibouti, only a few miles (kilometres) from the US facility, marking the first overseas base for Beijing's rapidly growing military.

White said she was "confident" that whoever had shone the high-powered lasers was Chinese.

Officials told The Wall Street Journal the laser likely came from the Chinese base.

The Federal Aviation Administration last month published a warning to pilots to use extreme caution in the area.

"There have been multiple lazing events involving a high-power laser in the vicinity," the warning reads.