Eighteen of the injured in Bocas del Toro province, on the border with Costa Rica, were in critical condition, the national emergency agency said in a statement.

The National Front for the Defence of Economic and Social Rights, a non-governmental labour umbrella group, identified the dead man as Antonio Smith, a banana union leader.

"Look at how many injured people are here. President, place your hand on your heart and sort this problem out because you are in power thanks to us Panamanians," Simon, a Changuinola resident, told the Reuters news agency.

Last month, Ricardo Martinelli, Panama's president, signed a law which limits the power of unions and gives companies the right to suspend the contracts of striking workers and hire replacements.

In a separate incident a day earlier, 48 striking workers on a $5.25bn project to widen and deepen the Panama Canal were fired and at least six were arrested after refusing to return to work.