Bulgaria's health minister has said that restaurants and bars will have to close at 10pm from September 7 while indoor sports competitions will be held without spectators as the country braces for a surge of new coronavirus infections, Reuters reports.

"There is no place for panic. The situation is serious, but not out of control. The low percentage of vaccinations forces us to impose these measures," interim health minister Stoicho Katsarov told reporters.

Under the new restrictions, which will be in force until the end of October, music festivals will be banned, while cinemas and theatres will have to operate at 50 per cent capacity.

Students will be allowed to attend classes when the school year begins on Sept 15, Katsarov said, but he warned that if the infections continue to rise, they may have to switch to online studies.