A Chinese submarine conducted a simulated missile attack on the USS Ronald Reagan aircraft carrier near Japan in October, a report said Tuesday.

Citing American military sources, online news service the Washington Free Beacon said the submarine shadowed the carrier and was detected behaving as if about to fire a cruise missile from a torpedo tube.

It said the U.S. Navy has briefed congressional staff on the matter, adding that Washington has kept the incident secret to avoid inflaming relations with Beijing.

“We have nothing to provide,” Cmdr. Bill Clinton, the spokesman for the U.S. 7th Fleet, told The Japan Times. The 7th Fleet is based in Yokosuka, Kanagawa Prefecture.

Clinton referred questions on the matter to the office of the United States Secretary of Defense in Washington. It is unusual for U.S. military spokespeople to deflect questions of this nature to the top of the command chain.

The Ronald Reagan is the United States' only forward-deployed aircraft carrier. It arrived at Yokosuka on Oct. 1 and later departed for operations in the South China Sea.

The Washington Free Beacon said the incident occurred on or around Oct. 24 off southern Japan, as the Reagan sailed from Yokosuka to the Sea of Japan in the company of several other U.S. warships.

It was unclear how long the alleged incident lasted. On Nov. 3, the news service cited an unnamed defense official as saying the submarine's presence set off alarm bells aboard the Reagan.