TEGUCIGALPA (Reuters) - Thousands of protesters took to the streets of the capital on Tuesday to urge Honduran President Juan Orlando Hernandez to step down, just days after he was forced to deny taking money from drug gangs to secure his election in 2013.

The premises of at least three businesses in the city were set on fire after protests turned violent, officials said, and riot police clashed with demonstrators while attempting to disperse the crowd with tear gas and water cannons.

“The narco must go, JOH must go!” protesters chanted, using the president’s initials, as they marched through central Tegucigalpa toward Congress.

A court filing was published late last week in which U.S. prosecutors alleged that Hernandez’s 2013 presidential bid had been partly funded by money from drug traffickers.

The document filed to the U.S. Southern District court of New York said the Hernandez campaign received $1.5 million from “drug proceeds” that were used to bribe local officials in exchange for protection and the completion of public works.

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Hernandez rejected the allegations, casting himself as the victim of a smear campaign by drug gangs he had targeted, and accusing political opponents, such as ex-president Manuel Zelaya, of colluding with gangsters to discredit him.

Protesters attacked police with sticks and stones near to Congress after officers deployed tear gas, and a Red Cross official said that five people were treated for injuries.

Fire service spokesman Cesar Trochez said “three commercial businesses caught fire” during the clashes, adding that the causes for the blazes were under investigation.

The demonstration against Hernandez was called by the Platform for the Defense of Education and Public Health, a coalition of trade unionists and public workers that have sought the president’s ouster over his plans for public services.

A conservative ally of the United States, Hernandez has come under increasing pressure since his younger brother Tony was arrested in Miami in November on drug trafficking charges.