United Kingdom officials on Friday raised the national threat level to "critical" after a bomb partially exploded aboard a train during the morning rush hour, injuring 30 and placing the country back on high alert after a series of devastating attacks earlier this year.
The threat level was last raised to critical following the Manchester Arena bombing in May, when 23 people, including the attacker, were killed as they exited a concert by U.S. popstar Ariana Grande.
In what authorities called a "very significant" development, officers arrested a man at about 7.50 a.m. (0650 GMT) in Dover, from where passenger ferries sail to France. Neil Basu, the Met Police's Senior National Co-ordinator for Counter Terrorism Policing, in a statement, said cops were working round the clock in an effort to hunt and trace the ones responsible for the bombing at the underground train.
Police swiftly declared a terrorist incident but have not confirmed any details of suspects after US President Donald Trump claimed the perpetrators were "in the sights of Scotland Yard".
Announcing the raised threat level, the Prime Minister said police had asked for authorisation to enact part of the first phase of a plan to provide military support to the police, known as Operation Temperer.
The suspect was being held for questioning under the Terrorism Act.
"Our embassy officials and staff have advised the members of the Filipino community to remain calm yet vigilant even as there are no reports of Filipinos injured in the explosion", said Presidential Spokesperson Ernesto Abella. Yesterday's bombing was the fifth terror attack in Britain since the beginning of 2017. We are not, at this time, changing our protective security measures and the steps taken to free up extra armed officers remain in place.
None of the injuries were believed to be life-threatening.
Detectives have so far spoken to 45 witnesses are receiving photos and videos from the public, while scouring CCTV footage.