Germany may need to close borders to neighbouring countries if they do not act to curb coronavirus infections, Merkel's chief of staff said on Thursday.

Helge Braun told ARD television it was important to get infection levels under control so that countries could protect themselves from new, more transmissible strains of the virus.

"The danger is that when the infections in a country go up, this mutation becomes a quasi majority variant and then the infection can no longer be controlled," he said.

"And therefore even stricter entry rules at our internal borders are unavoidable, and since everyone does not want that, it is important that we act together now."