Former federal Greens leader Bob Brown has been banned from entering Rwanda, after the African nation's government cited “contradictory messages” in his visa application.

Dr Brown received formal approval on October 30 to visit the war-torn African nation to support the local Greens party. He was due to depart on Monday before the government's about-face.

Bob Brown. Credit:Andrew Meares

“This is very unfortunate, not just for the Greens in Rwanda, but for democracy in a country where political opposition is not wanted by the government of president (Paul) Kagame,” Dr Brown said in Melbourne today.

"I will continue to support the Rwandan Greens and to work for people pursuing democracy under far more difficult circumstances than we experience in Australia.”

Critics of Rwanda's government say the country is an authoritarian state, with those who speak out persecuted and often killed.

In October, Rwanda controversially gained a non-permanent African seat on the United Nations Security Council.

This came despite a leaked UN report that claimed one of Rwanda's high-ranking officials was leading a violent militia uprising in the Democratic Republic of Congo.