(Changes to reflect source of tweet allegations against Rajab)

Bahraini human rights activist Nabeel Rajab arrives for his appeal hearing at court in Manama, February 11, 2015. REUTERS/Hamad Mohammed/Files

DUBAI (Reuters) - Bahraini human rights activist Nabeel Rajab will face trial for tweets he allegedly made about the Gulf Arab kingdom’s prison system and its involvement in the war in Yemen, his lawyer said on Sunday, and he could face up to 13 years in prison.

Rajab was arrested earlier this month on unspecified charges in what appears an escalating crackdown by the Sunni-led government that also included a court shutting down a main opposition society and a decision to strip the spiritual leader of the island’s Shi’ite Muslim majority of his citizenship.

The case appears to relate to tweets he is alleged by the authorities to have made last year in which he suggested security forces had tortured detainees in a main prison and on a military campaign in Yemen by a Saudi-led coalition which also includes Bahrain.

“He was notified of the referring of his case regarding Jaw prison and the Yemen war to the High Criminal Court for trial,” Jalila Sayed, Rajab’s lawyer, said in an e-mail to supporters.

“The first hearing will be on 12 July 2016. Nabeel may face up to 13 years of imprisonment if convicted in that case,” she added.

There was no immediate comment from Bahraini authorities regarding the case. Officials there deny systematic abuses of human rights and have accused the opposition of stirring sectarian hatred in the kingdom and serving the interests of their rival, Shi’ite Iran.

Rajab has repeatedly been arrested since 2011 pro-democracy protests mainly by Bahraini Shi’ites were repressed with help by Saudi Arabia.

The kingdom hosts the U.S.’s Fifth Fleet and is considered by Sunni-ruled Gulf kingdoms as a strategic bulwark against Iranian influence in the Arab world.

The Bahraini government drew U.S. and United Nations condemnation earlier this month when it announced the country’s top Shi’ite cleric, Ayatollah Isa Qassim, would be stripped of his citizenship and when it closed down al-Wefaq Islamic society.

It had accused both of being linked to Iran and of fomenting sectarian tensions in the island kingdom, charges they deny.

An administrative court began hearing a petition by the justice ministry to dissolve al-Wefaq but postponed the hearing until September to give the group time to respond to the charges.

On Sunday, the group’s lawyer said that the court has informed him it was advancing the date for the hearing to June 28.