DUBAI: Bahraini authorities have put imprisoned prominent Bahraini human rightsinfo-icon campaigner Nabeel Rajab through the mill over criticizing oilinfo-icon-rich Persian Gulfinfo-icon monarchies for spreading "extremism" in an article published in French daily Le Monde.

Rajab, who already faces 15 years in jail for his criticism of Manama's main ally Saudi Arabiainfo-icon, faces such probe into his writings for the second time in recent months.

At issue is a letter that appeared Tuesday in Le Monde in Rajab's name. In it Rajab denounced the Islamic Stateinfo-icon (ISIS) group and accused Gulf monarchies of failing to tackle the rise of its violent ideology.

"I am writing from a prison in Bahraininfo-icon where I expect to be tried for criticizing the bombing of Yemeninfo-icon by Saudi Arabia and for revealing the torture committed in the prisons of my country. For that I risk 15 years in prison," the letter reads. "My trial is not exceptional, it is ordinary. Thousands of Bahrainis are in prison for expressing criticism and protesting against the government."

Rajab also asks Franceinfo-icon and Germanyinfo-icon to reconsider their support for Gulf monarchies because they were fuelling Islamist extremism. "They claim to be allies in the battle against extremism while fueling the crisis."

Rajab was arrested in June for comments on Twitterinfo-icon that criticised Saudi Arabia's military operations in Yemen, according to Human Rights Watch.

Nabeel Rajab's incarceration comes amid an intense crackdown on dissent by the West backed totalitarian regime in Bahrain which is plagued by unrest since 2011 Arab Spring.

The courtinfo-icon dealing with the case has repeatedly ordered that Rajab, 51, remain in custody despite recurring healthinfo-icon problems for which he was briefly hospitalised in late June.

The next hearing in that trial is scheduled for December 28.Early Thursday, Bahrain's Interior Ministry announced an investigation into Rajab over the letter, which it said contained "false rumors and tendentious news that represented an abuseinfo-icon of the Kingdom of Bahrain" and other Gulf countries.

However Rajab is recieving widespread support from rights activists from around the worldinfo-icon.

"Nabeel Rajab's recent letters remind usinfo-icon of Martin Luther King Jr.'s 'Letter from a Birmingham Jail,'" said Husain Abdulla, executive director of Americans for Democracy & Human Rights in Bahrain, referring the U.S. civil rights icon's message on nonviolent protest. "Like King, Nabeel is a true champion of human rights."

Bahrain has said no one can be prosecuted for political views because of freedom of expression enshrined in the constitution.

But activists say Rajab already faces another charge over a letter published in The New York Times in September. A secular politician also briefly faced charges for speaking to The Associated Press in November during a visit by Britaininfo-icon's Prince Charles and wife Camilla.

Bahrain, home to the U.S. Navy's 5th Fleet and an under-construction British naval base, saw protests Wednesday after police clashed with residents of a besieged town that is home to country's top cleric Isa Qassim, who was stripped of his citizenship in June.

The police operation sparked an apparent warning Thursday from the Ashtar Brigade, a militant group that analysts say has claimed some 20 bombings in Bahrain since 2013. An online threat attributed to the group cautioned the government that "our finger is on the trigger."

Human Rights Watch meanwhile raised concerns about the detention of Sayed Alawi, an engineer at the telecommunications firm Batelco, who was held for five weeks without access to his lawyer or his family. Bahraini officials have alleged Alawi violated the country's anti-terrorism laws.