Police moved in to stop home fans attacking Belgrano supporters at the Marcelo Bielsa stadium in Rosario and used rubber bullets and truncheons to usher the visiting fans out of their stand with several minutes of the match still to be played.
Belgrano players attempted to calm their supporters only for some police officers to turn on them. Defender Gaston Turus suffered a deep cut below his left eye from a truncheon.
Newell's won 2-0, with their second goal coming in added time after the match had resumed following a 10-minute interruption.
"(Belgrano) repudiates, rejects and publicly and judicially denounces the pressure and generalised violence to which their supporters and professional squad were subjected to by Santa Fe (province) police," the club said in a statement.
It added that Belgrano and their supporters, from the neighbouring Cordoba province, as well as teams from other parts of the country regularly suffered ill-treatment at the major grounds in Santa Fe, including Rosario Central, Union and Colon.
"But is it only the police who are responsible? The Santa Fe provincial government knows this goes on. More than once we have presented statements and videos to (national governing body) AFA. They also know and we expect a solution.
"We won't cease in our repudiation, in denouncing all those involved and in the search for an end to the social and club violence that reigns at grounds, especially in Santa Fe province."
Belgrano president Armando Perez asked Rosario prosecutor Enrique Paz to take testimony from Turus, who had been refused the opportunity at a police station in Rosario where he was told he was being denounced for aggressive behaviour.
"I went to denounce an aggression (towards me) and I got my fingers painted," Turus was quoted as saying in local media in reference to having his fingerprints taken.
Rosario has been a hotbed of fan violence this year.
A friendly between the city's two big rivals Newell's and Rosario Central, relegated to the second-tier Primera B Nacional championship in 2010, was called off in January due to bomb attacks on the premises of both clubs.