A technical report released by the Department of Homeland Security on Thursday singled out Moscow as directing the ongoing effort that could give the hackers the ability to sabotage or shut down energy and other utility plants around the country.

It was the first time Washington named the Russian government as behind the attacks which have been taking place for nearly three years.

The allegation added to a series of accusations of political meddling and hacking against Russia that led to Washington announcing fresh sanctions against the country this week.

"Since at least March 2016, Russian government cyber actors ... targeted government entities and multiple US critical infrastructure sectors, including the energy, nuclear, commercial facilities, water, aviation, and critical manufacturing sectors," the report from the DHS Computer Emergency Readiness Team said.

DHS, together with the Federal Bureau of Investigation, said the Russian hackers targeted two groups -- the infrastructure operators themselves, and also peripheral "staging targets" which could be used as stepping stone into the intended targets.

Staging targets included third party firms supplying services and support to the main targets but may have less secure networks. The hackers had a deep toolbox of methods to enter target systems, they said.

The hacking effort paralleled Russia's alleged operation to interfere with the 2016 US presidential election and continue with online media manipulation throughout 2017.

DHS did not identify specific targets which the Russians broke into. But it said they were able to monitor the behavior of control systems, install their own software, collect the credentials of authorized users, monitor communications, and create administrator accounts to run the systems.

- Sustained attack -

The government has been issuing warnings to operators of US infrastructure -- power producers and distributors, water systems, and others -- about foreign hacking since 2016.

In January a White House report said cyberattacks cost the United States between $57 billion and $109 billion in 2016, and warned that the broader economy could be hurt if the situation worsens. It pointed the finger mainly at attackers from Russia, China, Iran, and North Korea.

Last September the private security firm Symantec outlined hacking efforts focused against US and European energy systems by a high-skilled group it dubbed Dragonfly 2.0.

"The Dragonfly group appears to be interested in both learning how energy facilities operate and also gaining access to operational systems themselves, to the extent that the group now potentially has the ability to sabotage or gain control of these systems should it decide to do so."

Symantec did not name the origin of the group, but the DHS report included Symantec's Dragonfly analysis in its allegations against Russia.

On Thursday the government announced sanctions against Russia's top spy agencies and more than a dozen individuals, citing both the election meddling and cyberattacks.

"We will continue to call out malicious behavior, impose costs, and build expectations for responsible actions in cyberspace," said Rob Joyce, the cybersecurity coordinator on the White House's National Security Council.