A 13-year-old boy buried under a collapsed Berlin apartment building was found dead on Wednesday after firefighters had dug with their bare hands through the night in a frantic effort to save him.

The bodies of two elderly people were discovered earlier."We have bad news - three people have been found dead in the rubble," Berlin police chief Hagen Saberschinsky told journalists at the scene.

Up to four more people were still feared buried in the debris of the four-story building, destroyed on Tuesday in a suspected gas ex-plo-sion.

Officials said the body of the boy, identified only as Sven, was recovered near the bottom of the building. His dog had been freed by rescue workers several hours earlier.

Rescuers had initially been hopeful of finding the teenager alive after hi-tech listening equipment detected a heartbeat in the rubble. The fire brigade had worked through the night using sniffer dogs, machinery and their bare hands.

Firefighters said recovery work at the site was likely to last all through Wednesday, hindered by the risk that further parts of the building could collapse.