Three men have been charged in the US over a Cold War-style Russian spy ring that spoke in code, passed information hidden in bags and magazines and tried to recruit people with ties to an unnamed New York City university.

The trio were directed by Russian authorities "to gather intelligence on, among other subjects, potential US sanctions against Russian banks and US efforts to develop alternative energy resources", according to a complaint filed in federal court in Manhattan.

Prosecutors say one defendant, Yevgeny Buryakov, posed as an employee in the Manhattan office of a Russian bank. The others, Igor Sporyshev and Victor Podobnyy, held low-level diplomatic positions.

Mr Buryakov, who is in the US on a work visa, was arrested in the Bronx on Monday, but the two other suspects were protected from prosecution because of their diplomatic status and are believed to have returned to Russia.

Between March 2012 until as recently as mid-September 2014, the FBI observed Mr Buryakov and Mr Sporyshev meeting 48 times in outdoor settings, the complaint says. Several of the meetings "involved Buryakov passing a bag, magazine or slip of paper to Sporyshev".

In intercepted telephone calls made to set up the meetings, the pair spoke about exchanging items "referred to as some non-specific ticket, book, list or other ordinary item (umbrella or hat)", the complaint says. They also "discussed their attempts to recruit US residents, including several individuals employed by major companies, and several young women with ties to a major university located in New York City".