Thirty-seven foreigners died during a hostage crisis at a natural-gas facility in eastern Algeria, according to Algerian Prime Minister Abdelmalek Sellal.
Sellal's comments are the first he's made since Islamist militants, on Wednesday, seized control of the gas field, capturing hostages, including many Westerners.
On Saturday, Algerian forces attempted to rescue the hostages but set off a bloody battle with the hostage-takers.
Previous reports had said 23 hostages died during the standoff, but Algerian authorities are now revising the death toll upwards.
Defense Secretary Leon Panetta initially said that U.S. officials were uncertain of how many Americans were at the plant or how many might have died during the botched rescue operation.
On Monday The Associated Press, citing a U.S. official, reported that a total of three Americans died during the hostage crisis, while seven survived.
On Saturday, President Obama condemned the hostage takers.
"The blame for this tragedy rests with the terrorists who carried it out, and the United States condemns their actions in the strongest possible terms," Obama said in a statement. "We have been in constant contact with Algerian officials and stand ready to provide whatever assistance they need in the aftermath of this attack."
According to Sellal, three terrorists involved in the attack were captured.
Sellal added that "the primary target" of the hostage-takers was a bus transporting foreign workers en route to an airport. The terrorists also sought to blow up the gas facility, he added.
Reports have suggested that the terrorists are from northern Mali, where an Islamist insurgency is fighting French forces who are backing the government.