Ukrainian authorities said the country's top security body and a national news agency had been hit by cyber attacks.
Unidentified sources launched denial of service (DoS) attacks which are intended to make a machine or network resource unavailable to its intended users, officials said.
Last week the country's telecommunications system had come under cyber attack, with some Internet and telephone services severed after Russian forces seized control of airfields and key installations in Ukraine's Crimea region.
Crime is at record low levels and this government is taking action to tackle the cyber threat, investing more than £850 million through the national cyber security programme to develop and maintain cutting-edge capabilities.
The National Crime Agency will include a new elite National Cyber Crime unit to target the most serious offenders and provide enhanced intelligence for CEOP so they can protect even more children from harm.
But we know we need to keep pace with criminals as they target the web and so we continue to consider ways to ensure the police and security services have access to communications data.
The NSPCC has welcomed a government drive to tackle cyber crime, after MPs warned today that the UK was "losing the war against online criminal activity".
Claire Lilley, safer technology lead at children's charity NSPCC, said: "It's vital that child abusers and other criminals do not view the internet as a wild west frontier where they can act with impunity.
"So it's good to see that the Government is taking cyber-crime seriously - in particular the issue of child abuse images being shared online."
Crime is changing and not falling at the rate that figures suggests, the chairman of the Police Federation of England and Wales said today, after an influential group of MPs found that UK was "losing the war against cyber crime" in a new report.
Steve Williams said:
It is extremely concerning that relentless cuts to policing are continuing at a time when there is a burgeoning cyber crime industry.
This report highlights how the Government message that its reforms are working because crime is falling is one which is over-simplistic and misleading. It is also rightly acknowledges that online crime can play a direct role in other offences being committed.
Crime is clearly changing, not falling at the rate the figures suggest, and an unknown but extremely high number of offences are going unreported. The police service needs greater, not fewer, resources to deal with the challenges of the 21st century.
The UK is being "too complacent" about online criminal activity because the victims are hidden in cyberspace, the chair of the Home Affairs Select Committee said today, after it issued a warning that the country was "losing the war on internet crime".
Labour MP Keith Vaz said:
The threat of a cyber attack to the UK is so serious it is marked as a higher threat than a nuclear attack.
You can steal more on the internet than you can by robbing a bank and online criminals in 25 countries have chosen the UK as their number one target. Astonishingly, some are operating from EU countries.
If we don't have a 21st century response to this 21st century crime, we will be letting those involved in these gangs off the hook.
The UK is losing the war against internet crime, an influential group of MPs has warned. Despite being the preferred target of online criminals in 25 countries, the UK is still "complacent" towards e-crime as victims are "hidden in cyberspace", the Home Affairs Select Committee said.
The group of MPs said sufficient funding and resources for tackling online crime, which includes Identity theft, industrial espionage, credit card fraud and child exploitation, has not been allocated.
Tougher sentences for online criminals and improved training for police officers are recommended by the Committee to deal with the growing threat of cyber criminality.