WASHINGTON • The US Treasury has imposed sanctions on three Russian individuals and five companies, saying they had worked with Moscow's military and intelligence services on ways to conduct cyber attacks against the US and its allies.

"The entities designated today have directly contributed to improving Russia's cyber and underwater capabilities through their work with the FSB, and therefore jeopardise the safety and security of the United States and our allies," Treasury Secretary Steven Mnuchin said on Monday, referring to Russia's Federal Security Service.

The designation blocks all properties of those targeted that are subject to US jurisdiction and prohibits American citizens from engaging in transactions with them.

Moscow had no immediate comment on the new sanctions.

The Treasury statement said Russia's "malign and destabilising cyber activities" included the NotPetya ransomware attack last year - which it said caused billions of dollars in damage and was part of the Kremlin's effort to destabilise Ukraine - and assaults on the US energy grid and Internet routers and switches.

"Today's action also targets the Russian government's underwater capabilities," the statement said. "Russia has been active in tracking undersea communication cables, which carry the bulk of the world's telecommunications data."

Monday's sanctions are the latest to hit Russian intelligence services.

The Obama administration sanctioned the FSB in December 2016, citing the Russian government's cyber operations aimed at the presidential election in the US that year. Washington imposed additional sanctions on the Russian intelligence services in March. Russia has denied trying to hack into other countries' infrastructure.

NYTIMES, REUTERS