A Zimbabwean pastor accused last year of trying to overthrow the government after helping launch protests against President Robert Mugabe has been arrested after flying home from the US.

Evan Mawarire was detained at Harare airport, according to his lawyer. He was charged with subverting a constitutionally elected government and would probably spend the night in custody, Harrison Nkomo said.

A police spokeswoman, Charity Charamba, said Mawarire had been apprehended on an outstanding arrest warrant. “He skipped the country but, as you know, going to America was never going to wash away his crimes. We were waiting for him to return,” she said.

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.

It was not immediately clear why Mawarire had been returning home. Some in Zimbabwe had criticised him for leaving the country amid the protests. At the time he said he feared for his family’s safety.

Before he left Zimbabwe, Mawarire was detained and initially charged with inciting public violence before prosecutors changed the charges.

A magistrate freed him after ruling that it was unconstitutional for prosecutors to bring the fresh charges to court.

Mugabe had said Mawarire and others should leave Zimbabwe if they were unhappy with the country’s situation. The economy has crashed and unemployment and frustration are widespread.