Concern over the appearance of a mysterious Russian satellite demonstrating "very abnormal behavior" is alarming some in the U.S., according to a State Department official.

"We don't know for certain what it is and there is no way to verify it," said assistant secretary Yleem Poblete at a conference in Switzerland this week.

Without detailing what the satellite’s abnormal behavior was, Poblete expressed concern that the object, which was launched last October, might be a weapon of sorts.

"[The satellite's] behavior on-orbit was inconsistent with anything seen before from on-orbit inspection or space situational awareness capabilities, including other Russian inspection satellite activities," Ms. Poblete told the conference on disarmament in Switzerland.

"Russian intentions with respect to this satellite are unclear and are obviously a very troubling development," she added, pointing to recent comments made by the commander of Russia's space forces, who said adopting new prototypes of weapons was an aim of the force.

Yet, Russia denies the claim, calling the comments “the same unfounded, slanderous accusations based on suspicions, on suppositions and so on."

According to Alexandra Stickings, a research analyst at the Royal United Services Institute, because so much of what goes on in terms of space-based capabilities is classified, it is hard to tell which technology could be in use.

When asked about the satellite, a spokesman for the U.K.'s Ministry of Defence said he could neither confirm nor deny any tracking of Russian satellites.

"There are a range of threats and hazards to all space capabilities in what is an increasingly contested domain," he said.

"These include the development of counter-space weapons by a number of nations.

"The U.K. is working closely with international allies, including the U.S., to re-enforce responsible and safe behaviors in space and to build knowledge, understanding and resilience."

To contact the author of this article, email mdonlon@globalspec.com