Panamanian banana workers protesting over a new law that weakens the power of labour unions have seized four police officers, according to the president's office.

The officers were taken hostage on Friday, the second day of violent confrontations between the striking workers and security forces in Changuinola in western Panama.

At least one man died on Thursday as police firing tear-gas and buckshot battled strikers who had blocked roads with felled trees and burning tyres.

Hospital authorities said 102 people had been treated for injuries by early on Friday.

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.