Several of the 179 residents have since been tested for the coronavirus, public health officer Marcus Kowalczyk said, adding that sequencing the samples to establish if they too had the Indian variant would take several days. 

Authorities around Europe are on high alert for the variant, which caused devastation in India before establishing a foothold in Britain. Infectious variants are a major threat to governments' ability to contain the pandemic. 

"It started suddenly on Sunday," said Ute Nicole Gaertner, a resident of one of the buildings, in Velbert, near Dusseldorf. 

"Suddenly council officials were everywhere and then we were locked in," she added, as residents looked down from their balconies. "It's terrible - I have four children, a very disabled child who needs therapy... It's a bit difficult here at the moment." 

The earlier spread of a variant that originated in Britain forced authorities in Germany to delay plans to soften lockdown rules earlier in the year. 

The number of confirmed coronavirus infections in Germany rose by 4,209 to 3,603,055, data from the Robert Koch Institute (RKI) for infectious diseases showed on Tuesday. 

The reported death toll rose by 221 to 86,381.