Suspect in attack arrested in London

LONDON (Reuters) British police arrested an 18-year-old man on Saturday in the southern port of Dover as they hunt for those responsible for the bombing of a London train that injured 30 people the previous day.

Prime Minister Theresa May placed the UK on its highest security level on Friday, meaning an attack could be imminent, and moved soldiers and armed police to secure strategic locations and hunt down the culprits.

In the fifth terrorist attack in the UK this year, a homemade bomb set off flames on a crowded rush-hour train in west London on Friday morning, but apparently failed to fully detonate.

In the explosion, some suffered burns and others were injured during the rush to escape the station, one of the network's non-underground stops. Health authorities stated that no one was in serious condition.

The Islamic State claimed responsibility for the attack.

"We made a significant arrest in our investigation this morning," said Neil Basu, Senior National Coordinator for Counterterrorism Policy.

"This arrest will lead to more activity from our officers," he said, suggesting there could be more arrests and home raids. "For investigative reasons, we will not give any further details about the man we arrested now."

The arrest was made in the port area of ​​Dover, where passenger ferries travel to France.

According to media reports, the bomb was attached to a timer, unlike the previous explosions, which were suicide bombs.

Photos showed a slightly charred white plastic bucket with wires sticking out of the top inside a supermarket shopping bag on the floor of a train car.

Parsons Green station, where the attack occurred, had already reopened on Saturday morning.

Armed police patrolled the streets of London near Westminster government departments and were expected to provide security for Premier League match venues on Saturday, including Wembley Stadium.

The last time the UK was placed on "critical" alert was after a suicide bomber killed 22 people, including children, at an Ariana Grande concert in Manchester in May.

The threat level remains at its highest for four days, while authorities race to determine whether the man acted alone or with others. Prior to this, the alert had not been triggered since 2007.