A series of loud explosions and heavy gunfire was heard at Nairobi's Westgate shopping mall Monday as dense black smoke billowed from the complex, an AFP correspondent at the scene said.

The area around the mall was teeming with Kenyan soldiers and armoured personnel carriers, as emergency workers and reporters were told to take cover.

Ambulances were also seen accelerating towards the scene.

The mall has been under siege by Al-Qaeda-linked Somali gunmen since Saturday in an attack that has killed at least 69 people, with another 63 reported missing.