Sen. Bernie Sanders (I., Vt.) said Wednesday that he did not know at the time that Russian trolls promoted his 2016 presidential campaign and wondered why Hillary Clinton's team did not do more to tell voters about the extent of Russia's election interference.

In addition to their well-known efforts to boost Donald Trump, Russian trolls supported Sanders' presidential primary campaign, when he mounted a surprisingly strong but ultimately unsuccessful challenge to Clinton, according to special counsel Robert Mueller's indictment from last week.

Mueller's team indicted 13 Russian nationals and three companies for interfering in U.S. elections from 2014 to 2016.

In an interview on Vermont Public Radio, Sanders took issue with a listener's question that made it seem as if he knew about Russian bots promoting his candidacy at the time he was running.

"If he was aware that Russians were trying to promote him and divide Democrats against Mrs. Clinton, why did he not communicate this to his supporters?" the listener asked Sanders.

"This was not supporting me any more than they were supporting groups like Black Lives Matter that are fighting for social justice," Sanders said.

"I did not know that Russian bots were promoting my campaign," Sanders added. "Russians bots were not promoting my campaign. What we found out is that in April and May, it appeared that there were lots of strange things happening, attacking Hillary Clinton."

The interviewer asked Sanders why he and his campaign did not tell his supporters about Russian interference if they knew Moscow was meddling to sow divisions.

"I would say that the real question to be asked is what was the Clinton campaign—they had more information about this than we did, and at this point, we were working with them," he responded.

"So did the Clinton campaign say, ‘Don't talk about this?'" the interviewer asked.

"No, of course not, but who do you think would be raising that issue?" Sanders said.

"I could see a world in which Mrs. Clinton said, ‘It's the Russians,' and Sanders supporters say, ‘Oh, that's baloney,' but if Sanders says it, they say, ‘OK,'" his interviewer said.

"We knew what we knew when we knew it, and that's about all that I can say," Sanders said.

"I did not know Russian bots were promoting my campaign." "The real question to be asked is" why the Clinton campaign didn't do something. — @SenSanders Listen live ➡️ https://t.co/lK28FIrEZ9 — Vermont Public Radio (@vprnet) February 21, 2018

Clinton pointed out in her book about her election loss, What Happened, that the Russians "made a particular effort to target voters who had supported Bernie Sanders in the primaries."