(Adds government comment, media freedom context)
KUWAIT, April 20 (Reuters) - A judge has suspended two Kuwaiti newspapers for two weeks after they published stories about a recording that discusses an alleged plot to overthrow the Gulf state's ruling system, their editors and the state news agency said on Sunday.
Kuwait, a major oil producer and U.S. ally, has imposed a news blackout on a sensitive investigation into the tape, saying earlier this month that media coverage about it was damaging to the country. A parliament session discussing the tape last week was held behind closed doors.
The Information Ministry said the newspapers had published "articles and views on the case which could affect relevant investigations by the Public Prosecution, and could even undermine the national interest," the KUNA news agency reported.
Al Watan editor-in-chief Sheikh Khalifa Ali al-Khalifa al-Sabah told Reuters that his publication would contest the decision and continue to update its website. It would not publish its print edition from Monday, he added.
"I do not think we talked about the tape more than any other newspaper," Sheikh Khalifa, a member of Kuwait's Al Sabah ruling family, said. "This is a great legal error."
Alam Alyawm editor Abdulhameed al-Da'as said his newspaper had also received a notice about the verdict on Sunday and would cease publication for two weeks.
Alam Alyawm is a separate publication to Al Watan and is close to Kuwait's political opposition. Its front page on Sunday said there was an "uprising against the closure of the newspaper," and featured comments from politicians and media figures against the expected suspension.
Kuwait's courts do not comment to the media about cases.
Reports about the tape have featured extensively in local newspapers and online since the start of the year, prompting a rare statement from the ruling emir's office this month, which told people to stop discussing the topic.
The public prosecutor opened a case into the tape in December after a legal complaint by a former parliament speaker who asked for an investigation into tweets about the recording.
Reporters Without Borders ranks Kuwait at 91 out of 180 territories in its 2014 World Press Freedom Index, above all other states in the six-nation Gulf Cooperation Council.
Kuwait is home to about a dozen daily newspapers, which often include criticism of government ministers, including some ruling family members. However issues related to the ruling system itself - a hereditary dynasty - are especially sensitive.
The 84-year-old emir, Sheikh Sabah al-Ahmad al-Sabah, came to power in 2006 after his ailing predecessor stepped down. Sheikh Sabah's brother, Crown Prince Sheikh Nawaf al-Ahmad al-Sabah, is next in line to become emir. (Reporting by Ahmed Hagagy and Sylvia Westall; editing by Jon Boyle)