"I want to assure the American people that the United States will take all necessary and proper steps that are required to deal with this situation," Panetta was quoted by the American Forces Press Service as telling the US reporters travelling with him on his current visit to Rome.
The US defense chief arrived in Rome Tuesday on a six-day trip to Europe to visit defense counterparts and troops.
He said the US strongly condemns these kinds of terrorist acts. "It is a very serious matter when Americans are taken hostage, along with others."
Panetta said he did not know how many Americans were being held by the terrorists, but noted that the US and British authorities -- the natural gas complex is partly owned by British Petroleum -- are in close consultation with their Algerian counterparts to learn as much as possible.
Panetta said he was not sure whether there was a link between the terrorist attack in Algeria and the French military operation in Mali, where France launched air strikes against militants that he identified as affiliated with al-Qaida in the Islamic Maghreb (AQIM).
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Stating that he had spoken with European government and defense leaders in Portugal, Spain and Italy about the situation in Mali, Panetta said: "I believe that there is a consensus that France took the right step here to ... deter AQIM from taking even further action there."
He noted that European defense ministers would hold a meeting Thursday to discuss ongoing assistance in Mali.