Secretary of State John Kerry said Thursday North Korea keeps making "very disturbing choices," apparently referring to its detention of another American citizen.

"This is obviously one of those moments when North Korea needs to figure out where it's heading and recognize that the United States of America is not engaging in belligerent and threatening behavior," he said, emerging from a Senate hearing, according to MSNBC television.

"These are all very, very disturbing choices by the North Koreans," he added.

The secretary was responding to a question about reports that an 85-year-old man named Merrill Newman has been detained in the communist nation since late October.

Newman, reportedly a Korean War veteran from Palo Alto in northern California, was on an organized tour.

His son Jeff told CNN that it's true that his father has been in detention there. 

The U.S. government has not formally confirmed whether Newman has become the second U.S. citizen to be detained in the North. Kenneth Bae, a 40-year-old Korean-American man, has been detained there for more than a year.

The State Department said Kerry was not directly mentioning a single case.

"Certainly, any time there are reports of Americans detained, that is a bad step and a bad move, which is what the secretary said," department spokeswoman Jen Psaki said at a press briefing.

Former New Mexico Governor Bill Richardson, meanwhile, is in touch with his North Korean contacts over the reported detention of Newman.

"Governor Richardson is involved in that he is in touch with his North Korean contacts," his spokeswoman Caitlin Kelleher said.

Richardson is known to have personal ties with some North Korean officials. (Yonhap news)