The mayor of London declared a major incident on Saturday as COVID-19 cases are rapidly rising in the United Kingdom’s capital. The surge comes as health officials worldwide express growing concern over the Omicron variant. 

“I’m hugely concerned about the surge of COVID-19 cases and rising hospital admissions across the capital,” Khan said on Twitter Saturday. “By declaring a Major Incident today, key agencies across London can better work together.”

According to the mayor’s office, a major incident is declared in the U.K. when an event or situation requires special arrangements to be implemented by emergency response agencies. It’s an incident that is “likely to involve serious harm, damage, disruption or risk to human life or welfare, essential services, the environment or national security,” the mayor said. 

The declaration will allow local authorities to reduce service disruption and allow more time to administer booster vaccines, Khan said. 

He previously declared a major incident on January 8 as COVID-19 cases in the city were “out of control.” It was terminated a month later, on February 26, as new infections gradually improved.

The latest declaration comes after London reported 26,418 new COVID cases over the last 24 hours, which is the highest number since the pandemic began, the mayor’s office said. Over the past seven days, the city reported 65,525 new confirmed cases and saw a 29% increase of patients hospitalized from COVID-19 complications in the same time period. 

Khan said officials are learning more about the quick-spreading Omicron variant. The strain has been detected in 89 countries since first being labeled a variant of concern on November 26 by the World Health Organization, the agency said. It is likely soon to become the dominant form of the virus in countries where the new variant is spreading locally, the WHO said. 

“The Omicron variant has quickly become dominant with cases increasing rapidly and the number of patients in our hospitals with COVID-19 on the rise again,” Khan said in a statement Saturday. “We are already feeling the impact across the capital.”

The mayor called on London residents to get vaccinated amidst the case surge. 

“We know that the vaccine offer our best defence against the virus,” he said. “There are now more clinics in London delivering vaccines than at any point during the pandemic. I urge all Londoners to book their appointment or to go to one of the many walk-in centres across the capital as soon as you can.”

Meanwhile, British travelers were left scrambling Friday after France announced it would ban all nonessential travelers going to and from the U.K. beginning at midnight.