Bangladesh, Feb. 20 -- A Russian national accused of concealing her connections to Moscows security services has pleaded guilty in a federal court in New York, bringing a dramatic and, at times, erratic chapter in a counterintelligence case to a close.

Nomma Zarubina, 35, admitted in court that she lied to the FBI about her contacts with Russias Federal Security Service, the Federal Security Service (FSB), and falsified information during her US naturalization process. The plea deal was entered before US District Judge Laura Taylor Swain in the Southern District of New York, after months of legal maneuvering and national security-related proceedings.

For observers of US-Russia intelligence tensions, the case illustrates the intersection...