The revelations came from three hostage-takers who were arrested after Algerian forces killed 29 other kidnappers, The New York Times reported Wednesday.
A senior Algerian official, speaking on condition of anonymity, said the three kidnappers provided the information under interrogation.
The plot to attack the gas production facility was hatched in northern Mali, where militant Islamists have taken control of the region and are being fought by Malian government and French forces. Other African nations are sending troops to help the government.
The Algerian official blamed the ongoing conflicts in North Africa on the Arab Spring, which he said had left large areas without governments, allowing extremists to flourish.
Algeria opposed intervention by Western democracies in toppling Libyan leader Moammar Gadhafi in 2011.
The militants who conducted the attack on the gas plant had traveled through Niger and Libya, whose border is only 30 miles from the facility, Algerian officials say. The militant who led the attack had purchased the group's weapons in the Libyan capital Tripoli, the senior official said.
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