Pakistan said in September 2011 it arrested al-Mauritani, better known in his homeland Mauritania as Youssouf Al Mauritani, during a joint operation with U.S. intelligence services.
Witnesses at the airport in Mauritania's capital, Nouakchott, saw a U.S. military plane deliver a prisoner late on Friday.
Mauritanian authorities confirmed al-Mauritani's identity, adding that he had been transferred from the U.S. military base in Bagram, Afghanistan.
"It's indeed Youssouf Al Mauritani, real name Abderhamane Ould Mohamed Al-Hussein," a senior security official told Reuters, asking not to be named.
"He was in Bagram and was handed over to the Mauritanian authorities by the Americans. He indeed arrived at the Nouakchott airport last night," he said.
A Mauritanian judicial official specialised in cases also confirmed that the prisoner transferred on Friday was al-Mauritani. U.S. embassy officials in Nouakchott declined to comment.
Pakistani military authorities said Al Mauritani was planning to attack U.S. economic interests including pipelines, hydro-electric dams and oil tankers when he was captured.