Guetersloh, home to some 100,000 people, and the neighboring town of Warendorf, became the first areas in Germany to fall back under lockdown measures that had been gradually lifted since the end of April.

State governor Armin Laschet, who had previously led calls for Germany to ease its lockdown restrictions, said bars, museums, galleries, cinemas, sports halls, gyms and swimming pools in Guetersloh and Warendorf would be closed, and picnics and barbecues prohibited.

"We will lift the measure as soon as possible, when we have certainty about the safety of the infection," Laschet told a news conference. "It is a preventative measure."

More than 1,500 workers at a meat processing plant in Guetersloh have tested positive for COVID-19, as well as some of their family members and 24 people with no connection to the plant, Laschet said. Some of those workers live in Warendorf, about 30 km (19 miles) to the west.

Laschet is a leading conservative contender to succeed Chancellor Angela Merkel when her fourth term in office expires next year. Further outbreaks of new coronavirus in his state, Germany's most populous, could damage his chances.

Germany's state premiers have agreed to act locally where possible to suppress the virus and there is no justification now for broader action, Laschet said.

Earlier on Tuesday, the head of the Robert Koch Institute for public health, Lothar Wieler, said local outbreaks had been a major factor behind a spike in the last few days in the coronavirus reproduction rate, currently estimated at 2.76.

A reproduction rate, or 'R', of 2.76 means that 100 people who have contracted the virus infect, on average, 276 others.

While Germany was at risk of a second coronavirus wave, Wieler said he was optimistic it could be prevented.