Rioters in Paraguay set fire to parliament late Friday to protest a bill that would allow the country's president to serve more than one term.
Protests erupted when the Senate secretly voted to amend the constitution, which has not allowed re-election since it was created in 1992 following the fall of a brutal dictatorship.
Demonstrators broke windows and set fire to the interior of the parliament building late Friday. One activist was reportedly killed by a blow to the head - what opposition leaders say was a rubber bullet fired by police.
"A coup has been carried out. We will resist and we invite the people to resist with us," said Senator Desiree Masi from the opposition Progressive Democratic Party.
In a statement released on Twitter, President Horacio Cartes appealed for calm, saying that "democracy is not conquered or defended with violence".
The bill will now move to the house, and if it passes, Cartes will be eligible for re-election in 2018 when his current five- year term ends. Former president Fernando Lugo, who was ousted in 2012 for his handling of a land eviction in which 17 people were killed, would also be allowed to run again.
A number of South American countries, including Paraguay, Peru, and Chile, have laws against presidents running for consecutive terms in a region not long removed from military dictatorships.