A team of Russian hackers called Cold River targeted three nuclear research laboratories in the United States last summer, according to five cybersecurity experts and internet logs reviewed by Reuters.

According to Internet records, between August and September of last year - during which time Russian President Vladimir Putin announced that his country might use nuclear weapons to defend its territory - the Cold River hackers targeted Brookhaven and Argon laboratories. Lawrence Livermore National Laboratories.

The records showed that the hackers created fake login pages for each of the three agencies, and emailed nuclear scientists to get them to reveal their passwords.

According to Reuters, it was not clear to her why these laboratories were targeted or whether any of the hacking attempts succeeded.

A spokesman for the Brookhaven Laboratory declined to comment, while a spokesman for the Argonne Laboratory asked to direct questions to the US Department of Energy, which in turn refused to comment.

The Cold River hackers have stepped up their hacking campaigns against Kyiv's allies since the start of Russia's war on Ukraine, according to cybersecurity researchers and Western government officials.

The attempted cyberattack against the US laboratories occurred when United Nations experts entered Russian-controlled Ukrainian territory to inspect the Zaporozhye atomic power plant, Europe's largest nuclear plant, and assess the risks of what both sides said could be a devastating radiological disaster amid heavy bombing nearby.

"This is one of the most important hacking groups you've never heard of," said Adam Myers, senior vice president of intelligence at the US cybersecurity firm CrowdStrike, adding that they are "directly involved in supporting the Kremlin's information operations."

The Cold River hackers first appeared on the radar of intelligence experts after targeting the British Foreign Office in 2016, and the group has since been implicated in dozens of other high-profile hacking incidents in recent years, according to interviews with 9 cybersecurity firms, according to Reuters.