Asuncion, Paraguay  - A former bishop, a woman and a former coup leader are the main candidates in Sunday's presidential election in Paraguay, in a historic vote that could cost the long-time ruling- party the presidency.

Paraguay has been governed by the Partido Colorado for 61 years, but according to opinion polls its candidate, Blanca Ovelar, is likely to come in behind former Roman Catholic Bishop Fernando Lugo, 56. General Lino Oviedo, a former coup leader, is tied with Overal for second place.

Polling stations are scheduled to open at 7 am (1100 GMT) Sunday and to close nine hours later. The results of exit polls are allowed to be made public as soon as voting is over.

A simple majority on election day will be enough for the winner to be elected to succeed outgoing President Nicanor Duarte Frutos, with a five-year mandate.

Ovelar drew some 80,000 people to her end-of-campaign address in Asuncion. The Colorados - who have ruled Paraguay since 1947 - have a solid party machinery. They have taken upon themselves large portions of state functions, notably in social assistance.

"Trust me. As a mother who knows what sacrifice means," she told supporters late Wednesday.

Lugo has claimed he will re-found Paraguay by fighting corruption and carrying out agrarian reforms in favour of poor peasants. Critics, including outgoing President Duarte Frutos, have accused Lugo of being aligned with leftist Latin American leaders like Venezuela's Hugo Chavez, Ecuador's Rafael Correa and Bolivia's Evo Morales. Lugo has denied this.

Some 2.8 million Paraguayans are entitled to vote Sunday. Beyond the president, they are to elect 45 senators, 80 provincial legislators, 17 governors and 400 district councillors, as well as the country's representatives in the regional Parliament of the South American trade bloc Mercosur.

Voting is compulsory in Paraguay for anyone aged 18-75.

The landlocked South American country set between Argentina, Brazil and Bolivia has a gross domestic product of 9.3 billion dollars, which grew by 4.5 per cent last year, although a large informal economy makes exact figures difficult. Paraguay exports primarily commodities and has profited from the surge in their prices in recent years.

It has a population of 6.8 million, of which over 1.5 million live in the capital, Asuncion, and its metropolitan area. (dpa)