(Adds writer comments in paragraphs 8-10)

RIYADH, March 15 (Reuters) - Saudi Arabia's most revered cleric said in a rare fatwa this week that two writers should be tried for apostasy for their "heretical articles" and put to death if they do not repent.

Sheikh Abdul-Rahman al-Barrak was responding to recent articles in al-Riyadh newspaper that questioned the Sunni Muslim view in Saudi Arabia that adherents of other faiths should be considered unbelievers.

"Anyone who claims this has refuted Islam and should be tried in order to take it back. If not, he should be killed as an apostate from the religion of Islam," said the fatwa, or religious opinion, dated March 14 and published on Barrak's Web site.

"It is disgraceful that articles containing this kind of apostasy should be published in some papers of Saudi Arabia, the land of the two holy shrines," he said, referring to Muslim holy places in Mecca and Medina.

"The rulers should hold these papers to account ... and all those who took part in the publication should know they were involved in the sin of heretical articles."

Barrak, who is thought to be around 75, is viewed by Islamists as the leading independent authority of Saudi Arabia's hardline version of Sunni Islam, often termed Wahhabism.

He said the articles suggested Muslims were free to follow other religions. Rights groups have accused Wahhabism of a xenophobic attitude which demonises other religions.

Abdullah bin Bejad al-Otaibi, one of the two writers, said he feared for his life and called on the government to intervene. The second writer was Yousef Aba al-Khail.

"My articles have been met with fatwas before but it never got to this level of directly inciting murder or directly accusing someone of no longer being a Muslim," he told Reuters.

"If this is allowed to pass, this country will be transformed into an arena of bloodshed. It will be chaos."

Saudi Arabia regularly executes drug traffickers, rapists and murderers, but it is rare for calls to be made to put people to death for opinions expressed in public.

Liberal reformers are engaged in a battle with religious hardliners over the direction of the country, a key U.S. ally and the world's biggest oil exporter.

Diplomats say powerful clerics allied to some key members of the Saudi royal family have prevented the government under King Abdullah from moving forward with social and political reforms. (Reporting by Andrew Hammond, editing by Summer Said and Mary Gabriel)