Chad has become the latest country to announce plans to withdraw from the International Criminal Court (ICC), saying that the court's effectiveness is "limited and uneven" and its activities focused on Africa.

It follows Venezuela, Burkina Faso, Mali and Niger in starting the process to pull out of the ICC, based in The Hague, which prosecutes individuals for war crimes and crimes against humanity.

ICC member states voted on Friday to dismiss prosecutor Karim Khan following disputed allegations that he sexually assaulted a female member of his staff.

Khan, 56, denies the accusations. His lawyer has said he will challenge "the lawfulness and fairness of the decision."

'Concentration on African countries'

Chad's announcement follows "an in-depth review of the functioning of the International Criminal Court since it began operating in 2002, as well as its record whose effectiveness remains limited and uneven," a government spokesperson said in a statement on Monday.

It also criticised what it said was a concentration of the ICC's activities on African countries.

Out of the 13 investigations launched by the court since it came into force, nine concern African states, as opposed to four opened in other regions of the world "but without any concrete progress," the Chadian government said.

"The court has only seven people in custody, six of whom are being prosecuted in African situations," it added.

USA's appeal

According to a statement on the foreign minister's official website last week, the decision to quit the ICC followed a request from the United States.

It said the US deputy secretary of state for African affairs had asked the Chadian government to reconsider its ICC membership during a telephone call on Thursday with the foreign minister.

"The American side expressed its concerns about the functioning of this institution and called on Chad to review its accession to the Rome Statute," a statement said.

However, on Friday Foreign Minister Abdoulaye Sabre Fadoul told AFP that "it was not at the Americans' request that we decided to withdraw from the ICC."

'Instrument of neocolonial repression'

On Friday, Venezuela said it was withdrawing over the court's perceived bias.

The announcement came amid an ongoing ICC investigation into alleged crimes against humanity committed under abducted Venezuelan president Nicolas Maduro's government.

Burkina, Mali, and Niger have called the court an "instrument of neocolonial repression in the hands of imperialism."

The ICC's executive body voiced concern earlier this month over the withdrawal of the three West African countries.