Defense Secretary Leon Panetta said Wednesday the U.S. "will take all necessary and proper steps" to deal with an Islamist attack on a natural gas field in southern Algeria that has resulted in Americans and other foreigners taken hostage.

Panetta would not detail what such steps might be after what he called a "terrorist attack."

A militant group that claimed responsibility says it's holding seven Americans, but State Department spokeswoman Victoria Nuland said she wouldn't provide details to protect those who were kidnapped.

Militants said they attacked and occupied the field partly operated by the energy company BP because of Algeria's support of France's operation against al-Qaida-linked Malian rebels groups to the southeast.

Panetta told reporters in Italy that he was briefed Wednesday on the Algeria attack and said the U.S. is in consultation with the Algerians to determine what the situation is and what happened.

Nuland said that Secretary of State Hillary Rodham Clinton spoke Wednesday by telephone with Algerian Prime Minister Abdelmalek Sellal.

U.S. authorities also were in contact with BP.

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Baldor contributed to this report from Rome.