The State Department issued a security alert for Algeria about one month after terrorists stormed the In Amenas natural gas facility in the country.
"There is a high threat of terrorism and kidnappings in Algeria," the warning read. "The U.S. government considers the potential threat to U.S. Embassy personnel assigned to Algiers sufficiently serious to require them to live and work under significant security restrictions."
A group associated with al-Qaida in the Islamic Maghreb, dubbed Those Who Sign in Blood, claimed responsibility for the attack. The State Department said the organization's leader, Mokhtar Belmokhtar, is a regional threat.
The January attack was said to be a response to an Algerian decision to let French forces use their airspace for a multilateral intervention in Mali, where al-Qaida occupies territory.
At least 37 employees of the companies working at the facility died in the attack and the raids that followed.