SAO PAULO, June 17 (Reuters) - At least 11 people have been killed in Brazil's southern state of Rio Grande do Sul after an extra-tropical cyclone struck the region on Friday, according to the state's authorities.

The storm caused torrential rains and helicopter searches are underway in flooded neighborhoods to find 20 others who have gone missing, the government of Rio Grande do Sul said in a press release.

One of the worst hit on the cyclone's trail was the town of Caraa, with a population of over 8,000 people.

"The situation in Caraa deeply worries us. It is essential that we can, in an organized way, quickly map the main affected areas and identify the people who need support," said Rio Grande do Sul's governor, Eduardo Leite, who visited the area.

As of Friday night, Maquine, a municipality on the eastern coast, had received around a foot of rain, authorities said.

Many residents in affected areas have taken shelter in outdoor sports facilities in their towns. The authorities have issued a warning for a risk of landslides in several areas.

Leite says authorities have carried out 2,400 rescues in the last two days.

"Our main objective at this first moment is to protect and save human lives. We are rescuing people who are stranded, locating missing people and giving all the support to the families," he said.

Deadly flooding in Brazil is common and has caused devastation for decades.