Amnesty International has said it fears for the safety of Pastor Evan Mawarire, who started the #ThisFlag protest movement against the regime of Zimbabwe's President Robert Mugabe.

Mawarire is currently in South Africa, where he has said he will remain for the foreseeable future after being publicly denounced by Mugabe.

Amnesty is encouraging supporters to write to Zimbabwean authorities urging them to ensure Mawarire's safety and wellbeing, reminding them states have an obligation to prevent abuses against human rights defenders and asking them "to end the harassment, arbitrary arrest and unlawful detention of human rights defenders and activists and perceived opponents of the ruling party ZANU-PF".

It says human rights defenders and activists in Zimbabwe have been receiving threats and are subjected to arbitrary arrests, ill–treatment and attempted abductions.

In an interview with Studio 7, Mawarire said he would return to Zimbabwe once he is assured of his and his family's safety.

"I have to ensure that my family and I are safe before I return home following President Robert Mugabe's address at the Heroes Acre where he accused me of being a fake pastor sponsored by the West," he said.

He added that after the president's remarks he has received threatening calls while in South Africa and people have been asking about his whereabouts, making him fear for his life.

The #ThisFlag campaign spread rapidly among social media users angry and frustrated at Zimbabwe's descent into poverty, lawlessness and economic chaos under Mugabe's inept stewardship. Mawarire was summoned to a Harare police station and arrested, accused of "incitement of public violence". He was freed on the same day when a magistrate dropped the charge. He has since received death threats and says he has fought off an attempted kidnap.