Updated at 3 a.m. Eastern, April 7, 2009:
Turkish officials have told the U.S. the man in custody is a "known fabricator" who has made various unsubstantiated claims in the past.
U.S. officials tell CBS News, "There was never a serious plot or threat against the President."
Turkish authorities told American officials the man never actually obtained an Al Jazeera credential, never gained access to any Presidential venue, and was in custody before Mr. Obama arrived in the country.
The Saudi Arabian newspaper al-Watan reported today that Turkish security services have arrested a man of Syrian origins Friday in connection with a plot to assassinate President Barack Obama during his current visit to Turkey.
The man, who was carrying an Al-Jazeera TV ID card in the name of M.G., confessed after his arrest that he was planning on stabbing the U.S. president with a knife during the Alliance of Civilizations summit held in Istanbul, adding that he had three other accomplices to help him execute his plan.
According to the paper, Turkish investigators were trying to verify whether the Qatari-based Arab TV channel has truly issued the ID card produced by the man, or if it's a forged copy.
The suspect, a permanent resident of Istanbul, has been regularly attending all conferences and events relating to the Middle East held in the city.
Al-Watan contacted Al-Jazeera's bureau chief in Ankara, Yucef al-Sharif, who said that news of the suspect came as a complete surprise to Al-Jazeera staff in Turkey, who all claimed that they knew nothing about the man.
"We learned that he (the suspect) claimed to be working for our bureau … if that has been the case then he most certainly forged our ID card," al-Sharif told al-Watan in a phone call from Ankara.
Al-Sharif said that Turkish security services know everyone who worked in Al-Jazeera's offices in Ankara.
Khaled Wassef monitors Arabic language media and jihadi Web content for CBS News.