The explosions were followed by volleys of gunfire, then a thick, dark column of smoke. Military and police helicopters and one plane circled over the Nairobi mall, giving the upscale Westlands neighborhood the feel of a war zone.
Security forces' efforts the previous day to rescue the unknown number of hostages inside failed despite the military announcing that "most" hostages had been saved. Kenyan officials have said preserving the hostages' lives is a top priority, greatly complicating the rescue effort.
From neighboring Somalia, spokesman Sheik Ali Mohamud Rage for al-Shabab _ the militant group that claimed responsibility for the attack _ said in an audio file posted on a website that the hostage takers had been ordered to "take punitive action against the hostages" if force was used to try to rescue them.
Military helicopters circled over the mall at daybreak Monday, when about five minutes of sustained gunfire broke out inside the mall, a clear indication that at least one of the estimated 10 to 15 gunmen who attacked the mall when it was filled with shoppers Saturday was still on the loose. A military ambulance then sped away from the scene.
A person with knowledge of the rescue operation told AP that no hostages had been released or rescued overnight Sunday. The person insisted on anonymity in order to talk about the rescue response.
At the Oshwal Centre next to the mall, the Red Cross was using a squat concrete structure that houses a Hindu temple as a triage center. Medical workers attended to at least two wounded Kenyan soldiers there on Monday.
Al-Shabab militants reacted angrily on Sunday to the helicopters hovering over the mall, and warned on Twitter that the Kenyan military action was endangering hostages.
A large military assault began on the mall shortly before sundown on Sunday, with one helicopter skimming very close to the roof of the shopping complex as a loud explosion rang out, far larger than any previous grenade blast or gunfire volley. Officials said the siege would soon end and said "most" hostages had been rescued and that officials controlled "most" of the mall. But on Monday the standoff remained.
As the crisis surpassed the 48-hour mark, video taken by someone inside the mall's main department store when the assault began emerged. The video showed frightened and unsure shoppers crouching as long and loud volleys of gunfire could be heard.
The al-Shabab extremists stormed the mall on Saturday from two sides, throwing grenades and firing on civilians.
Kenyan authorities said they would do their utmost to save hostages' lives, but no officials could say precisely how many people were being held captive. Kenya's Red Cross said in a statement, citing police, that 49 people had been reported missing. Officials did not make an explicit link but that number could give an indication of the number of people held captive.
Kenya's Red Cross said the death toll rose to 68 after nine bodies were recovered Sunday. More than 175 people were injured, including many children, Kenyan officials said.
Al-Shabab said the attack, targeting non-Muslims, was in retribution for Kenyan forces' 2011 push into neighboring Somalia.