"A squadron of heroic majahedeen was able to infiltrate deep into the Tunisian state and succeeded in kidnapping two Austrian tourists," Abu Mohammed said.
"The two kidnapped are in good health and are being treated well in keeping with the teachings of Islamic Sharia."
"We tell Western tourists flocking to Tunisia for leisure at a time when our brethren are being slaughtered in Gaza by the Jews with the complicity of Western states ... the apostate Tunisian state is not able, and will not be able, to protect you," the voice on the tape warned.
The Tunisian government said that there was no proof that the two tourists are still in the country.
"The authorities have begun carrying out intensive search operations by land and air," an official statement said.
It also stated that the two Austrians were last heard of crossing the Sahara desert in a direction that would have taken them out of Tunisia.
"Until now, there is no element that proves that the two Austrian citizens are in Tunisian territory or that they were kidnapped inside Tunisian borders," the statement added.
In the audio tape, the Al Qaeda spokesman did not make any specific demands as a condition for freeing the alleged hostages.
The Austrian foreign ministry has confirmed that a couple had been missing in Tunisia since mid-February.
Although not named by the government, press reports in Austria have named them as Wolfgang Ebner and Andrea Kloiber.
The Austrian government would only confirm that the man, aged 51 and a woman in her forties were last heard of in the village of Matmata in southern Tunisia.