Mausam Bora, a local resident, said that some of the marchers pelted shops and vehicles with stones, sparking a similar response from ethnic Assamese residents.
Bora said police opened fire on the crowd to quell the violence.
About 100 shops and several cars were damaged by the protesters, provoking residents to retaliate.
The state authorities have called in the curfew and imposed a curfew in some parts of the city.
Local media said the army has been called in to maintain order in Guwahati.