Brazilian state reels after its worst cyclone disaster
Watch: Deadly cyclone in southern Brazil kills 21 people
By George Wright
Torrential rain and winds caused by a cyclone have left at least 21 people dead in southern Brazil, with more flooding expected.
The governor of Rio Grande do Sul said it was the state's worst-ever weather disaster.
Thousands have been forced from their homes, officials said.
In Mucum, a town of 5,000 people, hundreds had to be rescued from their rooftops as 85% of the town was flooded, local media report.
President Luiz Incio Lula da Silva said the federal government was ready to help.
"Where there is a problem, the federal government will be there to save people from these problems," he said.