Mr. Sellal said the militants had expected to return to Mali with the foreign hostages. Seven French citizens taken hostage in recent years are thought to be held by al-Qaeda-linked groups in northern Mali.
The operation was led by an Algerian, Amine Benchenab, who was known to security services and was killed during the assault, he added. Mr. Sellal said negotiating was not impossible.
“They led us into a real labyrinth, in negotiations that became unreasonable,” he said.
Norway said five of its citizens from the plant were still unaccounted for, while Japan said three Japanese were still missing. Britain said three citizens and one resident were feared dead but not accounted for. Four Filipinos and two Malaysian plant workers were also missing, according to their governments.
• Associated Press reporters Bradley Klapper in Washington; Rob Gillies in Toronto; and Nicolae Dumitrache and Vadim Ghirda in Pitesti, Romania, contributed to this article.