Eight hours of nonstop rain left the city of 350,000 people largely under water, and forced authorities to evacuate the Jose Penna hospital.

Television images showed medical personnel evacuating babies from the hospital’s neonatal unit, and the army was deployed to assist in rescue efforts.

Some 1,000 people were evacuated to safety in the city about 600km south of the capital Buenos Aires.

Municipal officials said six people were confirmed to have died, but the toll could still rise.

The city received more than 400mm of rain in just hours – equivalent to what it normally gets in a year, “something unprecedented”, according to Javier Alonso, security minister for the Buenos Aires province.

“The biggest storm in Bahia Blanca was in 1930, with 175mm. This is almost three times bigger,” said Alonso.

Bahia Blanca’s airport was closed until further notice, and officials cut off part of the power supply to reduce the risk of electric shocks.

The provincial government said it was sending helicopters, canoes, ambulances and trucks bearing food, water and equipment to the stricken city.

The coast guard was assisting in the rescue with inflatable boats.

“It was raining, and suddenly we saw the street was flooded. About a meter-and-a-half of water came into my house,” Flavia Viera Romero, who rescued her children from the deluge, told the LN+ channel.