The accident happened in front of thousands of children

The accident occurred during a "test of strength" challenge to raise money for a hospital in Young, 380km (235 miles) west of the capital, Montevideo.

Contestants were pushing and pulling a train and two carriages when the vehicle gained speed and ran them over.

Local authorities have declared three days of mourning.

'State of shock'

Participants in the programme, called A Challenge to the Heart, raise funds for local charities by completing difficult tasks set by the network - in this case manoeuvring a train a certain distance down railway tracks.

The Associated Press news agency quoted Ana Portela as telling local radio station El Espectador that the train was moving when "somebody slipped and fell under the locomotive, and others were falling alongside it.

"There were shouts and somebody said 'my arm!'" Ms Portela said.

"Everybody was in a state of shock."

Graciela Baccino, a spokeswoman for Channel 10 television, said the tragedy was "deeply saddening".

She said the TV network offered its "solidarity and support" to the families involved.

About 3,000 schoolchildren were at the recording and witnessed the accident.