The Swiss National Bank is wary about cryptocurrencies like Bitcoin and Ether, Chairman Martin Schlegel said on Thursday, adding physical cash would retain an important role in the Swiss payments system in future.

"Bitcoin and other virtual currencies have grown enormously in recent years," Schlegel told an event organised by the Aargauische Kantonalbank in Brugg, Switzerland.

"But despite this growth, these currencies remain a niche phenomenon," Schlegel said.

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