KAMPALA, Uganda-- Three people were killed on Sunday when a building under construction in Kampala collapsed during a heavy rainstorm, but two children were pulled alive from the rubble, the Uganda Red Cross said.

Images posted on social media showed construction workers and passers-by digging through debris with their bare hands and firefighters using cutting equipment to saw through buckled metal in a bid to reach people feared trapped.

Red Cross spokeswoman Irene Nakasiita said three bodies had been pulled from the rubble of the four-storey building, while two girls aged five and nine had been rescued alive and taken to Kampala's main hospital.

The building is next to the usually crowded Kisenyi Bus Terminal, a key transit hub in the Ugandan capital.

Nakasiita said there were fears that motorcycle taxi riders and others may have sought shelter from the rain in the building and could be buried under the collapsed structure.

Rescue workers were still combing through the site as night fell, using two excavators. "The search and rescue continues," Nakasiita said.

Police spokesman Luke Owoyesigyire said the collapse of the building had covered "vehicles, motorcycles and workers" but that the number of people trapped had not yet been established.

Construction site accidents are common in Uganda, where health and safety regulations are lax.

In June, a stone quarry in Kampala collapsed, killing at least four workers.

In May, at least 15 construction workers perished when the building they were working on in the capital collapsed.