"On the basis of elements received so far from reliable channels ... [the ministry] can confirm that he is alive," the foreign ministry said in a statement, adding that it had "credible information on those who carried out the kidnapping".
"Contacts are ongoing in order to establish with certainty the intentions and expectations of the kidnappers, with a view to freeing Mastrogiacomo as quickly as possible."
Italy has nearly 2,000 troops in Afghanistan as part of a 35,000-strong Nato-led force.
The Taliban earlier said they would release Mastrogiacomo if he proved his innocence, but a spokesman said they later changed their mind after
"He is not a spy. He is a real journalist and I know that the people who kidnapped him know very well that he is a real journalist"
Alberto Negri, journalist
Italy's lower house of parliament overwhelmingly approved funding to keep the deployment in the country on Thursday.
On Saturday, Dadullah said: "Our spokespersons should be released and our news should be allowed to be disseminated without censorship."
One Taliban spokesman, Mohammad Hanif, was arrested in Afghanistan in January and another, Abdul Latif Hakimi, arrested in Pakistan in October 2005.
Mastrogiacomo has been missing in southern Afghanistan since last Sunday along with two Afghans, believed to be an interpreter and a driver or guide.
Dadullah said the Afghan driver among the trio had confessed to being an intelligence officer from the province of Helmand, where they were picked up, and to taking pictures of the Taliban stronghold where they were captured.
They were detained around the village of Bowlan, just outside the provincial capital Lashkar Gah, the commander said. The Italian is being kept in "one of our several headquarters in Helmand and is in good health".
The Taliban initially said the men were spies for the British military under the guise of being journalists.
"Nato has done what they wanted to do. Now they should just leave Afghanistan and let people live their lives without anybody's help"
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But at a news conference in Kabul, Italian journalists who have worked with Mastrogiacomo, including in Iraq and Somalia, rejected the charge.
Alberto Negri, a fellow Italian journalist, said: "Please release Daniele."
"He is not a spy. He is a real journalist and I know that the people who kidnapped him know very well that he is a real journalist."
A similar demand for the withdrawal of Italian troops was made when Italian photojournalist Gabriele Torsello was kidnapped in October in the same area by men who said they were with the Taliban.
A spokesman for the group denied they were involved.
Torsello was released three weeks later and said he had not seen daylight throughout his ordeal.