"Thirty-seven foreigners of eight different nationalities," were killed during the four-day siege, Sellal told a news conference in Algiers, without specifying their nationalities.
One Algerian also lost his life, bringing the giving an overall toll of 38, while five foreign foreigners were still missing, he added.
Among those that other official sources have already confirmed to have died in the siege were one Frenchman, one American, two Romanians, three Britons, six Filipinos and seven Japanese.
During the army's final assault on the plant, Sellal said the remaining gunmen executed several hostages by shooting them in the head.
The interior ministry had on Saturday given a preliminary toll of 23 foreign and Algerian hostages killed during the siege, which ended on Saturday with Algerian forces storming the remaining part of the complex still in militant hands.
The ministry said 685 Algerian and 107 foreign hostages were freed.
Sellal also said that the 32 militants who overran the In Amenas gas facility, taking hundreds of workers hostage, came from northern Mali. Twenty-nine of them were killed and three arrested.
He said the group's leader was Mohamed el-Amine Bencheneb, an Algerian militant known to the country's security services, and that he was killed during the army's assault.
As well as the three Algerians among them, the kidnappers had six foreign nationalities, namely Canadian, Egyptian, Tunisian, Malian, Nigerien and Mauritanian.