A Bahraini court denied bail for prominent human rights activist Nabeel Rajab as he went on trial on charges of insulting a state institution and neighboring Saudi Arabia online, his group said Wednesday.

The 51-year-old activist, who had been pardoned for health reasons last year, was rearrested last month as part of an intensifying crackdown on government critics that has drawn protests from the United Nations and key ally the United States.

Rajab appeared in court Tuesday and was charged with "insulting a statutory body, insulting a neighboring country and disseminating false rumors in time of war," the Bahrain Center for Human Rights said.

The accusations refer to tweets posted on his account in 2015, referring to "allegation of torture" at Bahrain's Jaw prison, and the Saudi-led military intervention in Yemen, the BCHR said.

Rajab has had recurring health problems and was briefly hospitalized late last month but the court ordered that he remain in custody throughout the trial and set the next hearing for August 2.

Amnesty International has said Rajab could face up to 13 years if convicted and has slammed what it described as a "farcical trial."

The Shiite activist has been repeatedly detained for organizing protests and publishing tweets deemed insulting to Bahrain's Sunni authorities.

He previously served two years in jail on charges of taking part in unauthorized protests in the Shiite-majority kingdom.

Home to the U.S. Navy's Fifth Fleet, Bahrain has been rocked by unrest since security forces crushed Shiite-led protests in 2011 demanding a constitutional monarchy and an elected prime minister.