Far-right anti-immigrant riots that flared in several United Kingdom towns and cities earlier this month could ignite again, the country's justice secretary warned on the weekend, as Prime Minister Keir Starmer canceled a vacation in order to focus on overseeing the response.

Justice Secretary Shabana Mahmood wrote in The Observer newspaper on Sunday that the situation remained tense and that police officers will continue to work hard to identify and arrest rioters and online agitators in a bid to fully restore order.

"If you stoke fear, or take part in violence, the full force of the law will be brought against you. Justice will be done," she wrote. "The impact of these days of disorder will be felt for months and years to come."

A spokesperson for the prime minister said on Thursday he had delayed his vacation in the wake of the riots, which began on July 30 and continued nightly until Aug 7.

Starmer's decision followed a YouGov poll that found 70 percent of respondents thought it was not the right time for him to take a break.

Starmer said on Friday it was clear many rioters had stopped attacking mosques and asylum seeker accommodation because of the lengthy prison sentences being handed to fellow agitators.

"We have to stay on high alert going into this weekend," he said. "We absolutely have to make sure that our communities are safe and secure and feel safe and secure."

Stephen Parkinson, the UK's director of public prosecutions and head of the Crown Prosecution Service, told the Sunday Times newspaper sentences of up to 10 years could be dispensed to rioters in the coming days.

By Saturday, police had arrested 779 people in connection with the unrest and formally charged 349 of them.

Parkinson said many more arrests and charges were expected in the coming days.

"As well as seeing a more significant number of charges coming through the system in the next few days, (prosecutions are) going to include more serious charges with stiffer penalties," he added.

The far-right riots began after three young girls were stabbed to death and several others were injured at a Taylor Swift-themed dance class in the northwestern England seaside town of Southport on July 29.

The suspect in that attack was incorrectly identified online as a radical Islamist asylum seeker. Police quickly pointed out that their 17-year-old suspect was not known to have been a Muslim and was born in the UK, but the unrest continued for several more days.

The riots seemed to ease last week due to a combination of online misinformation being countered, a huge police presence, counter-demonstrations from anti-fascist groups, and the deterring impact of long prison sentences.