Kamara spoke of "incomprehensible loss of control, the unannounced arrest and house searches" of the opposition before and after Friday's presidential poll.
He deplored the fact that "relatives and lawyers of the former Head of State and his associates have not been able to see them since their arrest."
Kamara appealed to the Mauritanian authorities to take "practical measures capable of defusing the political climate and easing the tension between the government and the opposition."
Ould Haidallah, one of the candidates who lost the Friday elections, was arrested on election eve and then released hours later.
He was re-arrested on Sunday on grounds that he had plotted a coup d'etat in case of a defeat in the elections.