BRASILIA, Sept 5 (Reuters) - An extratropical cyclone has been battering southern Brazil, flooding homes, swelling rivers and claiming the lives of nearly two dozen people, state authorities said on Tuesday.

Luana da Luz is among hundreds of Brazilians who have packed up their belongings in an effort to escape the rising waters.

"Since dawn, we saw that (the water) was going to flood (our house) and we were putting things on top of the table, on top of the wood stove, but it didn't help," said Da Luz, a resident of the town of Passo Fundo in the southern state of Rio Grande Sul, where state authorities have confirmed the deaths of 21 people.

An additional victim was confirmed in the neighboring state of Santa Catarina, according to local authorities.

Video obtained by Reuters showed houses in Mucum submerged by rising water, while streets and rivers were also flooded.

Dozens of homes had their roofs damaged by a hailstorm and hundreds of people are without contact in Rio Grande do Sul.

Brazil's federal government has announced some measures to respond to the disaster, and President Luiz Inacio Lula da Silva promised his government would do whatever is necessary to "save people from these problems."

"I feel devastated. I lost everything," said Dice Reginatto, from the city of Nova Bassano in Rio Grande do Sul. "There are many people who lost much more, but here at home I have nothing left."