Official Ukrainian websites have been knocked offline amid ongoing mounting tensions with Russia.
The official site of the Ukrainian parliament, government and foreign ministry were all inaccessible on Wednesday afternoon.
It comes a week after the country was hit by a huge distributed denial of service attack, which left many pages offline.
The government said it had been hit by a similar attack once again. The technique, known as DDoS, sees large amounts of traffic sent to certain websites or services to take them offline.
Ukrainian authorities said this week they had seen online warnings that hackers were preparing to launch major attacks on government agencies, banks and the defence sector.
Ukraine has suffered a string of cyberattacks that Kyiv has blamed on Russia. Moscow, which is caught up in a mounting confrontation with the West over Ukraine, has denied any involvement.
Additional reporting by Reuters