The African Development Bank (AfDB) said Friday its international staff had returned to Ethiopia, a month after their withdrawal following the assault of two staffers by security forces.

AfDB president Akinwumi Adesina met Ethiopian Prime Minister Abiy Ahmed in Addis Ababa at the end of last month, the bank said in a statement.

It has "subsequently received formal apologies from the prime minister on behalf of the government of Ethiopia, with firm assurances of the security and safety of the bank and its personnel", the Abidjan-based bank said.

On December 20, it said two of its Addis Ababa-based staff had been "unlawfully arrested, physically assaulted, and detained for hours without charge or any official explanation" at the end of October.

The bank did not identify the two victims.

But two diplomatic sources in Addis Ababa previously confirmed reports that the bank's Ethiopia director Abdul Kamara was one of them and that he had since left the country.

The AfDB said on Friday it was "delighted with and reassured by the strong personal leadership and firm commitment shown by Prime Minister Abiy Ahmed, which have led to the resolution of the impasse following the incident".

The bank was created in 1964 to finance development efforts in Africa.

Apart from countries of the African Union, its membership includes about 20 non-African nations.

Its investments in Ethiopia come to $1.24 billion covering 22 projects.