DOHA/WASHINGTON, June 3 (Reuters) - U.S. investigators are in Qatar to help Doha probe the alleged hacking of the Gulf Arab state's news agency website, a Qatari and a U.S. law enforcement official said, after an attack that had soured ties between Western-allied Gulf Arab states.

Qatar said last week that hackers had posted fake remarks by the emir, Sheikh Tamim bin Hamad al-Thani, that purportedly had him criticising some leaders of fellow Gulf Arab states and calling for an easing of tensions with regional foe Iran.

Gulf Arab states have rejected Qatar's explanation, leaving local media to unleash a barrage of attacks on the young emir, accusing him of cozying up to Iran.

The row erupted days after the first visit by U.S. President Donald Trump to Saudi Arabia, in which he sought to galvanise fight against Islamist militancy and Iran, which Washington sees as a threat to regional stability.

A Qatari official who asked not to be identified said that experts from the Federal Bureau of Investigation (FBI) had been helping with the probe since Friday.

In Washington, a U.S. law enforcement official confirmed that an FBI team was in Doha "working with Qatari authorities to investigate the alleged hacking incident into its state news agency".

The officials gave no details on the number of people on the U.S. team or progress in the investigation.

The FBI had no immediate comment on the report.

The rift has revived a 2014 row that erupted over alleged Qatari support for the Muslim Brotherhood and meddling in the affairs of fellow members of the Gulf Cooperation Counci (GCC).

Saudi Arabia and the United Arab Emirates, both members of the GCC, have labelled the group as a terrorist organisation.

Qatar's emir visited Kuwait this week in what appeared to be an attempt by Kuwait mediate between Doha on one side and Abu Dhabi and Riyadh on the other. There was no immediate sign of a breakthrough.

Saudi and UAE media on Saturday continued their criticism of Qatar. One newspaper posted a story citing about what it said were Qatari ties with Israel, using an old photo of the then Qatari Emir Sheikh Hamad bin Khalifa al-Thani shaking hands with the late Israeli President Shimon Peres.

Most Gulf Arab states have no official ties with Israel. Qatar briefly hosted an Israeli trade office but it was shut several years ago.



(Reporting by Tom Finn in Doha and Mark Hosenball in Washington; Writing by Sami Aboudi; Editing by Edmund Blair) ((Sami.Aboudi@thomsonreuters.com; +97143918301;))