"Most of the hostages have been rescued and security forces have taken control of most parts of the building," the Kenyan military said in an 11:45 p.m. post on Twitter.
The military tweeted that four of its personnel had been injured in the final assault to free the hostages at the Westgate Shopping Mall being held by Somali-based terrorist group al-Shabaab and were taken to a hospital for treatment, The Nation reported.
At least one terrorist was killed in the hostage-taking episode, Kenyan President Uhuru Kenyatta said. Prior to the final assault that began at 6 p.m., he had said besides one terrorist killed, between between 10 and 15 other terrorists were hiding in part of one building, Voice of America reported.
The Kenyan Red Cross said the number of victims rose to 68 after the bodies of nine more people were discovered. Scores more were wounded.
Witnesses said a large explosion shook the mall as an international force made an assault on terrorists.
USA Today reported the blast occurred after a Kenyan and international force launched the counter-attack to free the hostages, who had been held since the al-Shabaab militants took it over Saturday. Kenyan security forces were supported by police, Israeli forces and U.S. FBI agents, Kenya's The Daily Nation reported.
Officials weren't sure how many hostages remained inside the building, but estimated there were about 30 people holed up in one area with the shooters.
U.S. President Barack Obama on Sunday spoke to Kenyatta to express his condolences, a statement from the White House said.
"President Obama reiterated U.S. support for Kenya's efforts to bring the perpetrators of the attack to justice. The president also reaffirmed the strong and historic partnership between the United States and Kenya as well as our shared commitment to combating terrorism and promoting peace and prosperity in East Africa and around the world," the statement said.
Israel said a cafe in the mall was owned by an Israeli national, but it was not believed to be the main target of the terrorists. One Israeli was injured in the attack and three others escaped unharmed.
Al-Shabaab continued to crow on social media that its fighters were still active and holding Kenyan police and soldiers at bay.
"We know that they are now isolated somewhere within the building," Kenyan State House spokesman Zain Verjee told CNN.
The upscale shopping center remained sealed off Sunday as Kenyan forces warily searched the many shops and corners of the five-story facility. Shoppers who had been in hiding for hours were occasionally led from the mall to safety.
Al-Shabaab declared the attack was retaliation for Kenya's military support of the government in neighboring Somalia, which has been locked in a long struggle against al-Shabaab.
But Kenyatta told reporters the attack would ultimately be put down and his country would track down all of the conspirators. "We will punish the masterminds swiftly, and indeed very painfully," he said.
Kenyatta said his nephew and the nephew's fiancee were among those killed Saturday. The casualty list included several Americans, who were all among the injured.