Nine Zimbabweans have been arrested in South Africa after they were caught allegedly trying to leave the country to fight in the war between Russia and the Ukraine, police say.

The group, aged between 20 and 26, were arrested in and around Johannesburg by a multidisciplinary team on Sunday evening.

They were caught as they were "preparing to board flights out of the country", authorities added, but their final destination is unclear.

They have been charged with contravening South Africa's Regulation of Foreign Military Assistance Act, which outlaws mercenary activity without government permission.

Police said five people were arrested at South Africa's biggest airport, OR Tambo, and another four at a hotel in Bruma, east of Johannesburg by a multidisciplinary team that involved Interpol.

All nine later appeared in court, according to state prosecutors.

The police statement added that the involvement of Interpol and other international law enforcement agencies indicated that the suspects had also allegedly violated laws in their respective home countries, prompting cooperation with South African authorities.

They have also not said whether the group allegedly intended to fight for Russia or Ukraine nor provided details of the organisations allegedly involved in facilitating their travel.

Citizens of several African countries, including Kenya, Ghana and South Africa, have gone to fight for Russia in Ukraine - some they had been duped and had not realised where they were going.

A Ukrainian intelligence assessment estimated earlier this year that more than 1,700 people from 36 countries in Africa have been recruited to fight for Russia.

Kenya at the time estimated that 252 citizens had been illegally conscripted in Russia. In March, Foreign Minister Musalia Mudavadi visited Moscow to address the issue.

He said at the time that an agreement had been reached to stop recruiting Kenyan nationals.

In March, Zimbabwe said that 15 of its nationals had been killed after being recruited to fight for Russia in Ukraine, with more than 60 still trapped on the frontlines.

The previous month, South Africa secured the return of 17 South Africans who were allegedly tricked into joining the war.

In December last year, South African authorities arrested five people, including a journalist, for allegedly recruiting people to join the war.

Ukraine has also been recruiting foreign nationals, including from Africa.