Prague - US-funded Radio Free Europe/Radio Liberty says its news services have been disrupted in a cyber attack.
The Prague-based broadcaster says the intermittent cyber warfare began on Thursday.
It says the attackers have been using a distributed denial of service attack that floods the computer servers with fake traffic from numerous computers infected with malware. More details were not given.
The network experienced a similar but more limited attack in 2008.
It says other similar US media, including the Voice of America, Middle East Broadcasting, and the Office of Cuban Broadcasting services have also been affected by the attack.
Established in 1949, Radio Free Europe is a non-profit corporation that broadcasts to 21 countries, including Iran, Pakistan and Afghanistan.