KIEV, Ukraine: Many government websites in Ukraine have suffered cyberattacks, with the intruders posting the text, "Be afraid and wait for the worst."

Other posts said that users' personal information had been hacked.

Officials in Ukraine said that Russia was most likely behind the attack. Among the websites attacked included those of the Ministry of Foreign Affairs and other government agencies.

In a tweet, Oleg Nikolenko, Ukraine's foreign ministry spokesman, said that the "investigation is still ongoing but the Security Service of Ukraine has obtained preliminary indicators suggesting that hacker groups associated with the Russian secret services may stand behind today's massive cyberattack on government websites."

Meanwhile, Ukraine's communication intelligence service reported that as many as 70 central and regional authority websites were attacked.

Observers noted that the attacks come following a week of diplomacy involving NATO, the Organization for Security and Co-operation in Europe and bilateral talks between Russia and the United States, which sought to deescalate tensions on Ukraine's border.

"This is not the first time or even the second time that Ukrainian Internet resources have been attacked since the beginning of the Russian military aggression," the Ukrainian Information Ministry said in a statement.

Officials said most of the government websites have already returned to normal.

Meanwhile, the Security Service of Ukraine said in a statement that although "provocative messages were posted on the main page of these sites," the content of the sites was not changed, adding "the leakage of personal data, according to preliminary information, did not occur."

In a statement following the cyberattack, Josep Borrell, the EU's high representative for foreign affairs and security policy, said, "Such actions aimed at destabilizing Ukraine contribute to further escalation of the already tense situation."