London police have arrested an 18-year-old man suspected of being involved in Friday's subway bombing, which injured 29 people.
"We have made a significant arrest in our investigation this morning", Neil Basu, Senior National Co-ordinator for Counter Terrorism Policing, said in a statement. ISIS claims it was carried out by an affiliated unit.
"The threat level has been raised to critical, therefore we are reviewing our events and current demand".
UK Police said some 1,000 armed officers would be seen across the country after military assistance was requested.
A police manhunt led to a "significant" arrest in connection with an explosion in what officials called a terrorist attack on a crowded London subway auto.
Deaf community outraged after interpreter signed gibberish before Irma
Manatee County officials did not immediately respond to a request for comment from BuzzFeed News. The interpreter - a lifeguard named Marshall Greene - apparently has a deaf brother.
Basu advised the public to "remain vigilant" and said their "complex investigation" into the attack is ongoing.
A crude explosive, wrapped in a plastic bag that was concealed in a bucket, detonated during the morning rush hour in a train at the station.
No one has yet been arrested over the bombing, but anti-terrorism police chief Mark Rowley said the investigation was making "really good progress".
"The Metropolitan Police Service and British Transport Police attended the scene, along with colleagues from the London Fire Brigade and London Ambulance Service".
On Friday evening, the prime minister raised the threat level from worldwide terrorism from severe to critical - the highest level and an indicator that "an attack is expected imminently".
Police officers outside Parsons Green Station after the attack.
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