Human rights experts at the United Nations have called on Qatar to release a poet sentenced to 15 years in prison over verses considered offensive to the Gulf nation's former ruler.

A statement Tuesday said the sentence imposed on poet Muhammad ibn al-Dheeb al-Ajami in 2013 was "disproportionate and amounts to political censorship to art and expression."

Qatari officials could not be immediately reached for comment.

Al-Ajami faced specific charges over a poem posted online in 2010 that discussed the traits needed for a good leader — which apparently was seen by authorities as a challenge to Qatar's emir and ruling family.

He is more widely known for an Internet video of him reciting "Tunisian Jasmine," a poem lauding that country's popular uprising, which touched off the Arab Spring.