A Paraguayan opposition leader who alleged major fraud in last week's presidential election was arrested Friday for "disturbing public order," police said.

Paraguayo "Payo" Cubas, who came third in Sunday's presidential vote, did not resist arrest in San Lorenzo, outside the capital, Asuncion, Commander Gilberto Fleitas told reporters.

The detention of US-born Cubas was ordered by government prosecutors amid high tensions after the ballot.

Cubas had denounced alleged irregularities in Sunday's poll, which was won by right-wing candidate Santiago Pena with 42 percent of the vote, followed by center-left challenger Efrain Alegre with 27 percent.

Cubas garnered 22 percent of the vote, higher than expected. He has not filed any official complaint to back up his claims of a "monumental fraud."

Government authorities on Tuesday dismissed claims of fraud, with Pena urging calm in the face of protests called by Cubas.

In the capital Asuncion, several hundred Cubas followers had demonstrated Monday, clashing with police outside the electoral authority's headquarters.

"There is no possibility of fraud," electoral tribunal spokesman Carlos Ljubetic told reporters on Tuesday.

Pena's Colorado Party has governed almost continually since 1947 -- through a long and brutal dictatorship and since the return of democracy in 1989, but has been tainted by corruption claims.

Sunday's vote keeping the party in power bucked a recent anti-incumbency trend in Latin American elections with voters repeatedly punishing establishment parties, often in favor of leftist rivals.