The Kyiv Independent cited an unnamed source in Ukraine’s Main Intelligence Directorate (HUR) as saying the agency was responsible for launching the distributed denial-of-service (DDoS) attack, which comes in the wake of a spate of similar operations. Russian business news service Frank Media said several sources had confirmed that a cyberattack was in progress on Monday morning.

Online services of Gazprombank and Bank Zenit were also unavailable on Monday, the Kyiv Independent reported, with the situation further exacerbated by attacks on telecoms and internet networks.

"Broker applications, ATMs, Russian social media networks, messengers, Internet providers, and payment systems were also attacked," the paper quoted an anonymous source as saying.

Ukraine’s Euromaidan Press reported that the disruption to the central bank was caused by a major, week-long DDoS attack by HUR which had also affected Russia’s online financial services. The news service said the cyber-offensive was the most extensive against Russia to date and pointed out that the central bank is key to Moscow’s financing of its war in Ukraine.