Gunfire has been heard at the shopping complex in Nairobi where militants are believed to be holding hostages.
Sixty-eight people have been killed and more than 170 people injured since the attack began at 12:00 local time (09:00 GMT) on Saturday.
Between 10 and 15 attackers – thought to be militants from the Somali al-Shabab movement – are still inside the Westgate shopping centre.
Reporters at the scene said there had been heavy and rapid bursts of fire.
An unnamed Kenyan security source told the AFP news agency that an army assault was underway.
Some civilians are still trapped, either as hostages or in hiding.
