Consumer affairs centers received more than 2,000 inquiries over issues related to bitcoin and other virtual currencies last year, more than a threefold increase from the previous year, people familiar with the matter said Wednesday.

While cryptocurrencies have garnered a lot of public attention, the number signals that more people traded virtual currencies without adequate knowledge and, in some cases, incurred losses from price volatility.

The number of inquiries made at the National Consumer Affairs Center totaled 2,071 last year, compared with 616 in 2016 and 452 in 2015.

Bitcoin, which traded at around ¥100,000 in early 2017, briefly topped ¥2.3 million in December. It has recently fetched about ¥1.2 million.

"We want people to stop trading virtual currencies without understanding the transaction system and risks because it is dangerous," a consumer center official warned.

Among those who made inquiries, a man in his 40s reported that he had sent ¥400,000 to an account designated by a virtual currency company. But the company closed its business right after his payment and he was unable to confirm whether he actually purchased the currency.

Another man in his 50s reported that his virtual currency deposited at an exchange was traded by someone with unauthorized access. He said the exchange did not accept his claim over the phone and that he did not know what to do.