KYIV, Ukraine >> A series of cyberattacks today knocked the websites of Ukrainian government offices and major banks offline, Ukrainian authorities said, attacks that came amid strong tensions between Russia and the West over Ukraine.

It was too early to know, however, if the apparently low-level denial-of-service attacks might be a smokescreen for more serious and damaging cyber mischief.

Escalating fears about a Russian invasion of Ukraine eased slightly as Russia sent signals today that it might be pulling back from the brink, but Western powers demanded proof.

At least 10 Ukrainian websites were unreachable due to denial-of-service attacks, including those of the Defense Ministry, the Foreign Ministry, the Culture Ministry and Ukraine’s two largest state banks. In such attacks, websites are barraged with a flood of junk data packets, rendering them unreachable.

Customers at Ukraine’s largest state-owned bank, Privatbank, and the state-owned Sberbank reported problems with online payments and the banks’ apps.

“There is no threat to depositors’ funds,” the Ukrainian Information Ministry’s Center for Strategic Communications and Information Security said in a statement. The deputy minister, Victor Zhora, confirmed the cyberattacks.

The ministry suggested Russia could be behind today’s incident, without providing details. “It is possible that the aggressor resorted to tactics of petty mischief, because his aggressive plans aren’t working overall,” the statement said.

Oleh Derevianko, a leading private sector expert and founder of the ISSP cybersecurity firm, said it was not immediately clear if today’s cyberattacks were limited to a denial-of-service campaign.

“That’s exactly the question we always ask,” he said.

Ukraine has been subject to a steady diet of Russian aggression in cyberspace since 2014, when Russia annexed the Crimean Peninsula and backed separatists in eastern Ukraine.

The attacks follow a Jan. 14 cyberattack that damaged servers at Ukraine’s State Emergency Service and at the Motor Transport Insurance Bureau with a malicious “wiper” cloaked as ransomware. The damage proved minimal — some cybersecurity experts think that was by design, given the capabilities of Russian state-backed hackers. A message posted simultaneously on dozens of defaced Ukrainian government websites said: “Be afraid and expect the worst.”

Serhii Demediuk, the No. 2 official at Ukraine’s National Security and Defense Council, called the Jan. 14 attack “part of a full-scale Russian operation directed at destabilizing the situation in Ukraine, aimed at exploding our Euro-Atlantic integration and seizing power.”

Such attacks are apt to continue as Russian President Vladimir Putin tries to “degrade” and “delegitimize” trust in Ukrainian institutions, the cybersecurity firm CrowdStrike said in a subsequent blog post.

Ukraine has been the premier testing ground of cyberconflict. In the winters of 2015 and 2016, attacks on Ukraine’s power grid attributed to Russia’s GRU military intelligence agency temporarily knocked out power.

Russia’s GRU has also been blamed for perhaps the most devastating cyberattack ever. Targeting companies doing business in Ukraine in 2017, the NotPetya virus caused over $10 billion in damage worldwide. The virus, also disguised as ransomware, was a “wiper” virus that scrubbed entire networks.