Violence has broken out between government and opposition supporters who both claimed victory in Nicaragua's capital in local elections.
According to the opposition, several people were wounded and one person was killed.
Supporters of Sandinista candidate Alexis Arguello were seen attacking some 3,000 opposition supporters with sticks and stones as they marched toward a counting centre.
Three people were shot and wounded in the ensuing violence.
Nicaraguan police said four people were wounded by bullets but no one had died, after opposition leader Arnoldo Aleman said one person had been killed.
Early official returns showed Nicaragua's ruling Sandinista National Liberation Front ahead in around 100 of 146 municipalities, including the capital, after Sunday's elections, which were marked by violence and allegations of fraud.
But the opposition claims to have won in 58 municipalities, including Managua, and has denounced irregularities.
The government of President Daniel Ortega came under fire even before the polls for barring two opposition parties from fielding mayoral candidates and for police raids against non-governmental organisations.
Mr Ortega led Nicaragua from 1979 to 1990 after Sandinista guerrillas overthrew the Anastasio Somoza dictatorship. He was re-elected president in 2006.