The Zimbabwe pastor who fled to the United States after launching the #ThisFlag protest movement faces up to 20 years in prison for organizing protests against President Robert Mugabe in New York.

Evan Mawarire was arrested at Harare International Airport on his return home on Feb. 1 after having fled last year to the United States.

He is yet to appear in court, The Associated Press reported.

Last year Mawarire encouraged Zimbabweans on social media to hold protests against Mugabe, who turns 93 this month and is the world's oldest current head of State, a man who rules his country with an iron fist.

Zimbabwe authorities have charged Mawarire with subverting a constitutionally elected government, which carries up to 20 years in prison.

Mawarire backed a stay-at-home strike in July 2016, one of the largest anti-government protests in years, but he was arrested, only to be released when a court threw out the charges.

Lawyer Harrison Nkomo says the latest charges arise partly from his role in organizing anti-Mugabe protests during the U.N. General Assembly in September last year.

Mawarire is accused of organizing Zimbabweans "to converge in New York to confront the president of Zimbabwe," according to a police statement seen by The Associated Press and confirmed by his lawyers Feb. 2.

He left Zimbabwe for the United States in July last year after the regime detained him for publicly criticizing President Mugabe and mounting a social media campaign against him.

Amnesty International's Deputy Regional Director for Southern Africa, Muleya Mwananyanda, denounced Mawarire's arrest at Harare International Airport and his subsequent transfer to the Harare Central Police Station where he is being detained upon his return to the country.

"The trumped-up charge of subversion brought against Pastor Evan Mawarire this afternoon is absolutely ridiculous and a total sham," he said.

"Coming after a similar charge against him last year, it is designed to make him stop his human rights activism and to punish him for speaking out about the declining human rights situation in Zimbabwe.

"The authorities must immediately and unconditionally release Pastor Evan Mawarire, as he is a prisoner of conscience imprisoned solely for the peaceful exercise of his rights."

Mawarire was previously arrested on 12 July 2016 after he was charged with incitement to commit public violence under the Criminal Law Act for leading a national shutdown between 13 and 14 July 2016 against "corruption" and the declining economy.