Rwanda and Uganda have denied any deal with Israel to host thousands of African migrants told to leave that country in the next three months or face incarceration.

Israel this week called on migrants from Sudan and Eritrea to leave "to their country or to a third country," meaning Rwanda or Uganda. Those who leave before April will receive $3,500, airfare and other incentives. Many migrants say they fled conflict and persecution and seek refugee status. Israel calls them "infiltrators" and mostly economic migrants whose numbers threaten its Jewish character.

A Rwanda deputy foreign minister, Olivier Nduhungirehe, told The Associated Press (AP) his country has never reached any agreement with Israel on hosting asylum seekers.

Uganda's state minister for international relations, Henry Okello Oryem, also said there is no such agreement.

Prime Minister Benjamin Netanyahu has called the migrants' presence a threat to Israel's social fabric and Jewish character, and one government minister has referred to them as "a cancer," as reported by Reuters.

The vast majority came from Eritrea and Sudan and many said they fled war and persecution as well as economic hardship, but Israel treats them as economic migrants.

The plan launched this week offers African migrants a $3,500 payment from the Israeli government and a free air ticket to return home or go to "third countries", which rights groups identified as Rwanda and Uganda. "We have expelled about 20,000 and now the mission is to get the rest out," Netanyahu said.