Kiev, Mar 29 (IANS): Ukraine has neutralised a massive cyber-attack on core IT infrastructure that impacted the entire nation.

According to global Internet access tracker NetBlocks, the nation's online connectivity collapsed to 13 per cent, leading to the most severe Internet disruption registered in Ukraine since the invasion by Russia.

The Ukrainian Internet Service Provider Ukrtelecom was the target of a "massive cyberattack," the government said late on Monday.

According to the State Service of Special Communication and Information Protection (SSSCIP) of Ukraine, the cyber-attack had been neutralised.

"The first cyberwar in human history is under way," said SSSCIP Chairman Yurii Shchyhol.

The "entire IT-community of the world" is united against Russia's invasion, he added.

"In order to preserve its network infrastructure and to continue providing services to Ukraine's Armed Forces and other military formations as well as to the customers, #Ukrtelecom has temporarily limited its services to the majority of private users and business-clients," the SSSCIP posted on Twitter.

Ukrtelecom was slowly resuming Internet services.

"Our main challenge today is the victory over the enemy on all the battlefields, including cyberspace," the SSSCIP said.

"Every one of us can help in this fight by following the rules of cyber hygiene -- not to open unknown messages, not to download the files whose origin is not clear, to treat critically all the incoming information," it added.

Ukraine has been the victim of Russia-sponsored cyber attacks since the February 24 invasion.