State Department spokeswoman Jessica Simon said in an interview with RFE/RL that the attack was "another example of the assault against free and independent media in Belarus."
The cyberattack began on the morning of April 26 and knocked out eight of RFE/RL's broadcast services' websites. Although it is still unclear who was behind the attack, the chief target appears to be the website of the Belarus Service.
The "denial of service" (DOS) attack began while RFE/RL journalists in Belarus were preparing coverage of protests in Minsk marking the 22nd anniversary of the Chornobyl nuclear disaster. DOS attacks can render a targeted website unavailable to users, normally by flooding the site with fake requests to communicate.
What all these attacks have in common, Simon said, is that they deny the country's citizens the news they need to understand the world they live in.
Simon called upon the Belarusian government to take the necessary steps to end this kind of attack against RFE/RL.
Opposition websites in Belarus, including Charter 97 and the European Radio for Belarus, were hit at the same time as RFE/RL.
Nina Ognianova, the program coordinator for Europe and Central Asia at the New York-based Committee to Protect Journalists (CPJ), said it's the responsibility of the government of Belarusian President Alyaksandr Lukashenka to find and punish those responsible.
Ognianova said that in the current digital age, forces that she described as "enemies of the free press" always manage to find new, more sophisticated ways of silencing independent media and crushing dissent.
"In Belarus especially, RFE/RL service is significant now more than ever because Lukashenka's regime has destroyed the other independent and opposition broadcasters," Ognianova said. "So we certainly are very concerned about this short-lived but successful attack on RFE/RL."
Ognianova called on the authorities in Belarus to mount an investigation into who initiated the attack on the RFE/RL websites and to prosecute them vigorously.
All the affected RFE/RL websites are back online again.