Freedom Watch founder Larry Klayman, right, and former Sen. Gordon Humphrey, R-N.H., say it's possible the NSA was listening to their phone call Sunday. (AP)

Larry Klayman, the conservative legal activist who won an injunction against the National Security Agency's bulk collection of phone records, says a Sunday phone call with former Sen. Gordon Humphrey, R-N.H., had an unusual glitch.

Klayman, a former Reagan administration prosecutor, says an abnormally long list of numbers appeared when Humphrey called.

"It was as if you were calling outside the country – there were all sorts of weird codes [on the screen]," Klayman says. "It was '011,' then it was the number, then there were four numbers on the end of the number."

Humphrey called Klayman using an AT&T cellphone that has a New Hampshire area code. He didn't notice anything unusual about the call, but says he wouldn't be surprised if the NSA was listening.

"I assume I'm being monitored – I'd be naive to think I'm not being monitored," Humphrey says. "If whatever Larry saw was in some way related to that, I wouldn't be surprised. I have no way of knowing, of course."

Humphrey emailed NSA whistle-blower Edward Snowden in July to express his support for leaks that revealed the NSA's massive phone and Internet surveillance programs. He also attended a Nov. 19 rally in Washington, D.C., where Klayman called for a peaceful "Second American Revolution" and threatened to convene a "government-in-waiting" if President Barack Obama did not resign before Black Friday.

The former senator – in office from 1979 to 1990 – says his emails with Snowden and with Glenn Greenwald, the former Guardian reporter who broke many NSA surveillance stories, may have gotten him surveilled.

Klayman, the founder of Judicial Watch and Freedom Watch, has made other allegations about the possibility the NSA is "messing with" him.

During a Nov. 18 hearing before U.S. District Court Judge Richard Leon, Klayman said colleagues received text messages he did not send. Leon granted a preliminary injunction against the NSA's phone program – which the judge called "almost Orwellian" – on Dec. 16, but stayed his decision pending appeal. Klayman said last month his Yahoo emails were appearing six years out of date.