Gambia and Burundi are following South Africa in an attempt to exit the ICC, citing bias by the Court against African countries.
Amnesty International says the disconnect from the International Criminal Court is a blow to millions of victims of human rights abuses.
The ICC, which opened in 2002, is the first legal body with permanent international jurisdiction to prosecute genocide, crimes against humanity and war crimes.
Amnesty's west and central Africa spokesman, Steve Cockburn, says a move away from the Court would be a step back for justice in Africa and around the world.
"The International Criminal Court has been set up to protect people across the world, including in Africa, from the worst crimes: crimes against humanity, genocide, torture, rape; and anything that undermines that institution could end up being a denial of justice for people who have been victims of such crimes."
Gambia has joined Burundi and South Africa in announcing an intention to depart from the court, based in The Hague in The Netherlands.
South Africa says the tribunal's obligations are inconsistent with the country's laws, which give sitting leaders diplomatic immunity.
Justice Minister Michael Masutha says South Africa's plans to leave follow criticism for ignoring a court order to arrest a visiting Sudanese President accused of genocide and war crimes.
He says a written notice to withdraw has been submitted to the United Nations Secretary General.
"The withdrawal will take effect one year after the Secretary-General has received the notification. South Africa will remain obligated under the Rome Statute for the duration of the 12 months notice period."
An international lawyer at the Southern Africa Litigation Centre, Angela Mudukuti, says the withdrawal will result in a massive justice gap.
Ms Mudukuti says the court is the only current framework where crimes against humanity can be dealt with.
She says she fears the movement to leave the ICC will continue to grow.
"South Africa may have perhaps triggered an avalanche of withdrawals, as we see there's talks of withdrawals in Gambia, in Burundi. And I think given that Gambia and Burundi have unfortunately a very dark human rights record and so it's almost no surprise that initiation for a withdrawal has come from that side, but for South Africa, it is very surprising. And if nations like this seek to pull out of the Rome Statute, what more for other countries where human rights have no place?"
Burundi has sent a letter to UN Secretary-General Ban Ki-moon initiating its departure.
Burundi MP Gabriel Ntisezerana says the Court has a history of bias against Africans.
"By ratifying the Rome agreement introducing the International Penal Court, it was believed this court would be impartial. But we found that there are crimes committed in the world, especially in European countries, yet only Africans are pursued. We find that this court is being biased. It only condemns the countries of one continent while there are other crimes committed elsewhere that are not being punished or prosecuted."
Gambia's leader also confirmed the country is pulling out, repeating the accusation of bias.
Information Minister Sheriff Baba Bojang says the ICC targets the continent.
"This action is warranted by the fact that the ICC, despite being called the International Criminal Court, is in fact an 'International Caucasian Court' for the prosecution and humiliation of people of colour, especially Africans."
Amnesty International has dismissed suggestions of colour bias, saying the Court represents the only avenue of justice.
Steve Cockburn says he hopes other states will look to regional leaders, such as Botswana, who have opted to work constructively with the Court.
He says a mass African exodus isn't the answer.
"We hope that other African states would not follow this example and would instead engage with the International Criminal Court to take up any issues they might have with the court rather than withdraw."
All but one of the nine countries where the ICC has opened investigations are in Africa.
