Al-Merrikh suffered a 3-1 defeat at the hands of the defending African champions on Friday, which also ended their hopes advancing to the quarter-finals.
The Sudan outfit have now taken the decision to relieve the former Newcastle United and Leeds United star of his duties with immediate effect.
Clark took responsibility for Friday's defeat to the Red Devils and praised Mosimane.
"We were behind after the first half, and then we successfully equalized," Clark said, as per KingFut.
"Unfortunately, Al Ahly then took the lead with two goals in two minutes, and in a game like this, it's hard to score three goals.
"I am proud of my players and what they did, I am responsible for the result.
"Mosimane is a very good manager, he led Al Ahly to two consecutive Champions League titles."
