Traffic came to a halt on one of Reynosa's busiest roads following reports of a deadly shootout outside a popular store.
It all happened outside a Walmart store off Bulevar Hidalgo around 2 p.m. Monday.
Reynosa residents turned to the social media network Twitter to report the fatal firefight.
Tamaulipas state officials confirmed arrests in operations nearby but did not offer any immediate details about the shootout.
Residents reported at least five gunmen were killed in the shootout with Mexican soldiers.
Social media users posted pictures of the slain gunmen on Twitter and Facebook.
Action 4 News will provide more information as it becomes available.