Zimbabwe police have arrested 18 political activists, taking some of them off a plane in the latest clampdown by the government after warning it would crush opposition protests ahead of its hosting of a meeting of the southern African heads of state this month.

The Zimbabwe Lawyers for Human Rights group said it was representing the activists, who were detained on Wednesday.

Among the activists arrested is Namatai Kwekweza, a 25-year-old pro-democracy campaigner and the inaugural winner of the Kofi Annan NextGen Democracy Prize in 2023. The prize is awarded by the late United Nations secretary-general’s foundation to young people committed to the principles of democracy.

Amnesty International has condemned the arrests, while Mr Annan’s foundation said it was “deeply concerned” by the incident.

Ms Kwekweza and three other activists were removed from a plane on the tarmac of the Robert Mugabe International Airport in the capital, Harare. Another 14 activists were arrested the same day for holding a protest in another town.

The four taken off the plane are being charged with disorderly conduct for being part of a court protest in late June demanding the release of 77 opposition party members who have been in pre-trial detention for more than six weeks.

The 77 activists were arrested at a barbecue at the house of one of their leaders. Police said they gathered “with the intent to promote violence, breaches of peace or bigotry.” A mother and her one-year-old baby were among those detained.

President Emmerson Mnangagwa, who took over from autocrat Robert Mugabe in a coup in 2017, has been accused of cracking down on political opposition in a similar way to Mr Mugabe, who had led the country for 37 years since independence.

Numerous opposition members, university students and labor unionists have been arrested since Mr Mnangagwa, 81, became president.

He denies being oppressive but has warned the opposition against what he has called inciting violence. Authorities have moved to subdue any new protests ahead of the meeting of southern African leaders in Harare on August 17.

Mr Mnangagwa, Zimbabwe’s first lady and others were sanctioned by the US earlier this year for alleged involvement in gold and diamond smuggling and human rights abuses.