MANAGUA (Reuters) - Nicaragua’s main business lobby urged President Daniel Ortega to hold early elections to steer the country out of weeks of destabilizing protests, which again sparked deadly clashes on Wednesday, a human rights groups and local media said.

In a letter to Ortega published on Twitter, business association COSEP urged the 72-year-old president to bring forward the next vote at a date to be agreed between the government and representatives of civic society.

“Given the magnitude of this crisis, we urge you to undertake every effort in your power to find a peaceful solution before we find ourselves immersed in an even more tragic situation,” the letter said.

The next presidential election is scheduled for 2021.

Ortega told supporters that Nicaragua “is not private property” in response to the COSEP demand, according to local newspaper La Prensa.

Proposed changes to Nicaragua’s social security system last month triggered student-led protests and violent clashes.

Indignation at the crackdown in which dozens of people have been killed and over 800 injured has become a daily challenge to the rule of Ortega, a former Marxist guerrilla leader.

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Local media said there were more casualties in Nicaragua on Wednesday, after a march in the capital Managua, organized as a demonstration against the recent deaths, came under fire.

One man died and other people were injured after shots were fired on marchers, said Marlin Sierra, director of the local human rights organization CENIDH. Three other people also died in violence in the northwest of the country, Sierra said.

It was not immediately clear who had fired on the march. La Prensa blamed the attack on supporters of Ortega.

Erika Guevara-Rosas, Americas director for Amnesty International, said on Twitter that Ortega’s “violent repression has reached extreme levels” after the attack.

A Cold War antagonist of the United States who served a single term as president during the 1980s, Ortega returned to power in 2007. He was re-elected by a landslide for a third consecutive term in 2016 with his wife as vice president.

The Organization of American States last week called for early elections, but Ortega has not acceded.