Britain's interior minister said on Monday the country's terrorism threat level had been raised from "substantial" to "severe", the second-highest level, meaning an attack is highly likely, following Sunday's deadly blast in Liverpool. Prime Minister Boris Johnson said the Liverpool attack was a "stark reminder of the need for us all to remain utterly vigilant". Russ Jackson, in charge of counter-terrorism policing in northwest England, said the motive for the Liverpool attack was unclear. The explosion came just minutes before a Remembrance Sunday service at nearby Liverpool Cathedral, prompting speculation the event was the intended target. Watch this report for more.