Cheikh Ould Mohamed Ould Mkheitir, 36, had been initially sentenced to death, but was then given a jail term on appeal.
Moroccans joined in with Algeria's Africa Cup celebrations along their closed border, with many seeing the unity as a reminder to politicians on both sides to rethink their border policy.
Medecins Sans Frontieres (MSF) said it was an 'outstanding contradiction' for migrants to be released from the unsafe centre, only for more to be brought in just days later.
Libya's GNA said it cannot protect migrant detention centres from airstrikes such as those witnessed on Tuesday, amid reports hundreds remain vulnerable in the centres after the attack.
Mauritania opposition supporters arrested during clashes in the days following a disputed presidential election have been released following official confirmation of the ruling party's victory.
Mauritania remains on a knife-edge after last week's controversial election.
Mauritanian police raided the headquarters of two opposition parties, closing one of them, amid high tension followed a disputed outcome to presidential elections.
An Egyptian sports anchor has been mocked on social media for asking a football fan from West African state Mauritania where he learnt to speak Arabic.
Government candidate and frontrunner Mohamed Ould Ghazouani has declared himself the winner of the first round of Mauritania's presidential election, after 80 percent of the votes had been counted.
Some 1.5 million people will head to the polls on Saturday, with many hopeful that the West African nation will see its first democratic transition of power since independence.