"We do have reports of a missing American," a US Embassy spokesperson said.
"We are working with local authorities to find him and are in touch with his family." .
The US State department in Washington confirmed a US citizen had been reported missing in Saudi Arabia by his family, but declined to confirm he had been kidnapped.
"We heard that an Islamic website was making a claim but we have had no direct contacts with any organizations or persons claiming responsibility," State Department spokesman Stuart Patt said.
"We are not releasing the individual's name. He is a private US citizen, living in Saudi Arabia. His family reported him missing."
If confirmed, this would mark the first kidnapping of an American in Saudi Arabia.
Reuters reported that the US embassy report came on the heels of a purported al-Qaida statement that appeared on an Islamist website.
The statement, allegedly found on the "Sawt al Jihad" website, claimed that al-Qaida fighters kidnapped a US engineer to avenge abuse of Muslims in Iraq.
The statement included a passport-size photo of a brown-haired man and a business card with the name Paul M. Johnson and claimed the man was an Apache helicopter engineer born on 8 May, 1955.
The website carried identity cards
allegedly belonging to the captive
A copy of the man's passport, Saudi driving license and business card were also displayed on the website.
The statement alleged that the man was "one of four top Apache helicopter engineers" and that "these planes have long been used by Americans and their Zionist allies...in killing Muslims".
The man would be treated in the same way "the Americans dealt with our brothers in Guantanamo and Abu Ghraib," the statement said.
Claim of responsibility?
"The Mujahidoun were able in the same operation to kill
another American working as a manager in the military sector," the statement went on to say.
"They stalked him and then they killed him in his home," the
statement signed by "al-Qaida Organisation in the Arabian
A US national was shot dead in Riyadh on Saturday, the US embassy said.
In Washington, the US State Department said the man's identity was still not known. Washington has urged its citizens to leave Saudi Arabia.
"Those Americans who choose to remain here should exercise the utmost caution as they go about their daily lives," US ambassador to Riyadh, James Oberwetter, said in a statement.