CAIRO, Nov 27 (Reuters) - An Egyptian-born German author and critic of Islam who went missing has turned up safe and well, a security source told Egypt's state news agency MENA.

Hamed Abdel-Samad, author of "The Downfall of the Islamic World: A Prognosis", was reported missing by his brother this week, triggering speculation he might have been abducted after a cleric declared him an infidel and called for his death.

However, MENA said Abdel-Samad had returned to his hotel in Cairo without any injuries. It said he accused the owner of a plastics factory and an accomplice of kidnapping him over a financial dispute.

In a television show broadcast in June and posted on YouTube, the Egyptian cleric called for the killing of the author, who frequently appears in German media as a speaker on Islamic affairs, saying he was an infidel. ($1 = 0.7374 euros) (Reporting by Shaimaa Fayed; Editing by Alison Williams)