Ethiopia has repatriated more than 100,000 of its citizens from Saudi Arabia following a violent crackdown on illegal immigrants, Addis Ababa's foreign ministry has said.

Ethiopian Foreign Minister Tedros Adhanom said on Thursday that up to 50,000 more citizens were still expected to return.

"Last night arrivals from Saudi reached 100,620," Tedros said in a written statement, stressing that all the citizens that were detained in Riyadh deportation camps are back.

Ethiopia started repatriating its citizens from Saudi Arabia last month after a seven-month amnesty period for undocumented immigrants expired, sparking violent protests between Ethiopian migrants and Saudi police.

Foreign ministry spokesman Dina Mufti said repatriation efforts had been "successful so far and that the number is increasing over time.

According to the Ethiopian government, three of its citizens were killed in the clashes with Saudi police while protesters did not have a permit to demonstrate, but that arrests had been made though the number was not stated.

However, Human Rights Watch has urged Saudi authorities to launch a probe into the violence, and warned of a potential humanitarian disaster for workers held in custody.