Families and colleagues of missing workers at the site of a collapsed high-rise in Bangkok waited anxiously on Saturday as rescuers searched for survivors.

Authorities say dozens remain unaccounted for after the 33-storey building, which was under construction, gave way on Friday when a 7.7 magnitude earthquake struck neighbouring Myanmar.

Rescue crews used dogs to search for signs of life in the debris at dawn.

Families of the missing waited nearby, hoping for news of relatives who had been working at the site when the quake hit.