Zimbabwe's president has arrived in South Africa for his first official state visit in more than 20 years.

President Robert Mugabe arrived with his wife, Grace, on Tuesday at the Waterkloof air force base outside the capital Pretoria.

The Department of International Relations and Cooperation said in a statement that the purpose of Mugabe's visit is to strengthen economic cooperation.

The statement said the two country's presidents will sign an agreement to increase trade. South Africa's exports to Zimbabwe amount to about $2 billion dollars, while in contrast Zimbabwe exports goods worth about $170 million to South Africa.

Mugabe has visited South Africa on other occasions, such as presidential inaugurations and the state funeral of South Africa's first black president, Nelson Mandela in 2013.