Nov. 10 (Bloomberg) -- Nicaragua's police chief appealed for calm and dispatched anti-riot forces after clashes broke out between supporters and opponents of President Daniel Ortega on the streets of Managua.

Backers of opposition parties, claiming that Ortega's Sandinistas rigged yesterday's municipal elections, pulled down government campaign signs and hurled rocks, according to images broadcast on local television.

Constitutional Liberal Party leader Arnoldo Aleman, who served as president from 1997 to 2002, said at a press conference today that at least one person was killed. Police Chief Aminta Granera told reporters that forces were being mobilized to contain the violence.

The municipal elections were viewed as a referendum on Ortega's encore term as president. He had vowed to reconcile the country's past divisions since retaking office in January 2007.

His candidates pledged to lower food costs and fight poverty with programs funded partly by foreign aid, while the opposition vowed to spur employment and attract outside investors who remain nervous about Ortega after the economy crumbled during his first term, from 1984 to 1990.

Sandinista mayors and deputy mayors hold a lead or have won outright in 94 of 146 townships after a nationwide vote yesterday, according to preliminary electoral board results presented today.

`Manipulations' Alleged

The Constitutional Liberal Party, which picked up the most municipal seats after the Sandinistas, have denounced voting ``manipulations'' by Ortega's government and threatened to contest the results in court.

Sandinista candidate and three-time world boxing champion Alexis Arguello is leading the polling results for mayor of Managua, according to the Supreme Electoral Council.

Domestic election observers and opposition parties have reported ``widespread irregularities'' in the voting, U.S. State Department spokesman Robert Wood said.

``Unfortunately the Supreme Electoral Council's decision to not accredit credible domestic and international election observers has made it difficult to properly assess the conduct of the election,'' Wood said at press briefing in Washington today. ``We urge the government of Nicaragua to ensure that the official election results accurately reflect the will of the Nicaraguan people.''

To contact the reporter on this story: Eric Sabo in Managua, Nicaragua at esabo1@bloomberg.net.

Last Updated: November 10, 2008 17:20 EST