WASHINGTON—National Security Agency officers on several occasions have channeled their agency’s enormous eavesdropping power to spy on love interests, U.S. officials said.

The practice isn’t frequent — one official estimated a handful of cases in the last decade — but it’s common enough to garner its own spycraft label: LOVEINT.

Spy agencies often refer to their various types of intelligence collection with the suffix of “INT,” such as “SIGINT” for collecting signals intelligence, or communications; and “HUMINT” for human intelligence, or spying.