FILE PHOTO - Ahmed Mansoor, one of the five political activists pardoned by the United Arab Emirates, speaks to Reuters in Dubai November 30, 2011. REUTERS/Nikhil Monteiro

DUBAI (Reuters) - Amnesty International called on Wednesday on the United Arab Emirates to release a local activist who has been on hunger strike for more than three weeks, citing concern over his health and prison conditions.

Emirati campaigner Ahmed Mansoor was sentenced to 10 years in 2018 for criticizing the government on social media in a case that has drawn criticism from the United Nations and international rights groups.

“We are greatly concerned that his lengthy hunger strike would result in the deterioration of his health,” Amnesty International said in a statement.

The rights group said Mansoor was being held in solitary confinement. It urged the UAE authorities to ensure his detention conditions comply with international standards and that he be granted regular access to his family and medical care.

The UAE government media office did not immediately respond when asked to comment.

Mansoor, an electrical engineer and poet, was among five activists convicted of insulting the UAE’s rulers in 2011. They were pardoned the same year.

He was arrested again in March 2017 on charges of publishing false information and rumors, promoting a “sectarian and hate-incited” agenda, and using social media to harm “national unity and social harmony” and damage the country’s reputation.

He was one of a tiny number of publicly active rights campaigners in the UAE, a trade and tourism hub that tolerates little public criticism.

In 2015 Mansoor received the Martin Ennals Award for Human Rights Defenders, an annual prize awarded in Geneva by a panel of international human rights organizations, for his work documenting the human rights situation in the U.S.-allied Gulf Arab state.