https://www.bbc.com/news/technology-45194333

A mysterious Russian satellite displaying “very abnormal behaviour” has raised alarm in the US, 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 on 14 August.

She voiced fears that it was impossible to say if the object may be a weapon.

Russia has dismissed the comments as “unfounded, slanderous accusations based on suspicions”.

The satellite in question was launched in October last year.

“[The satellite's] behaviour 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, citing recent comments made by the commander of Russia’s Space Forces, who said adopting “new prototypes of weapons” was a key objective for the force.

Ms Poblete said that the US had “serious concerns” that Russia was developing anti-satellite weapons.

Alexander Deyneko, a senior Russian diplomat, told the Reuters news agency that the comments were “the same unfounded, slanderous accusations based on suspicions, on suppositions and so on”.

He called on the US to contribute to a Russian-Chinese treaty that seeks to prevent an arms race in space.