The international CEO of Good Governance Africa (GGA) Chris Maroleng and three of his colleagues were deported from Zimbabwe just days before the elections.
The GGA said in a statement released on their website that the group had been in the country for "only two days" when their "illegal" deportation took place.
Maroleng said his team was given permission to enter the country beforehand by officials at the Zimbabwean embassy in Pretoria.
"GGA was in Zimbabwe to conduct field research on election conditions and challenges, with several interviews set up with high-profile stakeholders in Harare and Bulawayo, the statement said. Zimbabwean immigration officials arrived at their hotel in Bulawayo, saying that they're doing a routine inspection of their passports.
"They then summoned us to their offices and asked questions about the reasons for our visit to the country. I explained our research objectives. About an hour later we were told we had to leave the country immediately. They escorted us back to the hotel and then to the airport," Maroleng said.
The thinktank said they were "shocked and dismayed ... but not surprised, as the pattern of bullying, anti-democratic behaviour by the ZANU-PF-led government – especially in the run-up to elections – is well documented,” he said.
Maroleng said he had decided, along with GGA's partners in Zimbabwe, to lodge a legal appeal against the decision to eject the team.