British Prime Minister Boris Johnson said on Sunday tougher lockdown restrictions were probably on the way as COVID-19 cases keep rising, but that schools were safe and children should continue to attend where permitted.

COVID-19 cases in Britain are at record levels and the increase in numbers is fuelled by a new and more transmissible variant of the virus. The government has cancelled the planned reopening of schools in and around London but teaching unions want wider closures.

Much of England is already living under the toughest level of restriction under a four-tier system of regional regulations designed to stop the spread of the virus and protect the national healthcare system.

But, asked in a BBC interview about concerns that the system may not be enough to bring the virus under control, Johnson said restrictions "alas, might be about to get tougher".

"There are obviously a range of tougher measures that we would have to consider I'm not going to speculate now about what they would be,” he said.

(With input from agencies)