Organization of American States (OAS) representative Emma Mejia highlighted on Sunday the large voters' participation in Paraguay's general elections.
"A positive impression is the high flow and calm of voters," said Mejia.
"I am surprised by the massive participation," said Mejia some hours after the elections had started.
OAS officials plan to visit at least some 200 voting booths during Sunday's elections, said Mejia.
Mejia said the OAS mission at 13:00 local time will emit a communique about its evaluation of the electoral process.
Polling stations opened at 7:00 a.m. (1100 GMT) and are scheduled to close at 5:00 p.m. (2100 GMT). Preliminary results will be announced at 9:00 p.m. (0100 GMT Monday).
About 2.8 million Paraguayans have registered to vote Sunday. They will choose their president, vice president, 45 senators, 80 lower house deputies and 17 governors, as well as the country's representatives in the regional Parliament of the Common Market of the South (Mercosur).
Voting was monitored by 80 observers from the Organization of American States headed by former Colombian Foreign Minister Emma Mejia.