The United States embassy in London has issued a security advisory urging American citizens in the UK to exercise increased caution, following the British government’s decision to raise its national terror threat level to “severe.”

In guidance issued on Friday, the embassy advised US nationals to stay alert in public areas and avoid locations such as schools, places of worship, tourist sites and major transport hubs, accordingto a report by Al Jazeera.

It also recommended that citizens vary their travel routes and timings to reduce predictability and maintain a low profile while moving around the country.

The warning comes after the UK’s domestic security service, MI5, confirmed that the Joint Terrorism Analysis Centre had upgraded the national threat level from “substantial” to “severe” — the second-highest category, indicating that an attack is considered highly likely within six months.

MI5 said the UK has been facing a gradual increase in terrorist threats over time, adding that the decision also followed a recent stabbing incident involving two Jewish men in the Golders Green area of London, though it stressed the move was not based solely on that attack.