The recent surge in the price of bitcoin, the cryptocurrency which has skyrocketed in value 20-fold this year, is "abnormal," Bank of Japan Governor Haruhiko Kuroda said Thursday.

Asked about whether he thought a bitcoin bubble was forming, Kuroda said at a press conference following the central bank's policy meeting, "It's not my place to say, but if you look at the charts, it's clear that the jump (in prices) is abnormal."

Bitcoin is "being traded for investment or speculative purposes," he said.

Kuroda also said there was a crucial difference between the cryptocurrency and conventional currencies such as the U.S. dollar and the yen. Unlike conventional currencies, bitcoin is not controlled by a central bank or government.

"If you're asking if bitcoin has the same function as currency, as a means of payment or settlement, the answer is no," Kuroda said.

The cryptocurrency, created through a process called "mining," traded at around 100,000 yen ($880.70) in January but jumped above 2 million yen for the first time on a major Japanese exchange earlier this month.