The service said four towns in the state of Santa Catarina have been cut off due to flooded roads. Many of those killed were crushed by landslides.
Over 160,000 people have been left without electricity. Natural gas supplies were cut off in the south of the state after a pipeline was damaged by rains.
A state of emergency has been declared in the region, and President Luiz Inacio Lula da Silva has pledged urgent federal assistance.
Brazilian meteorologists have warned that rains are expected continue this week.