Officials have issued a formal diplomatic complaint and demanded Beijing investigate a series of incidents dating back several weeks, spokeswoman Dana White said.

"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 Lemmonier 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 (kilometers) 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.