An 18-year-old man has been arrested in Dover on the morning of 16 September in connection with the Parsons Green terror attack.
London's Metropolitan Police have issued the following statement:
The 18-year-old man was arrested by Kent Police in the port area of Dover this morning, Saturday, 16 September, under section 41 of the Terrorism Act.
The man remains in custody at a local police station. He will be transferred to a south London police station in due course.
Deputy Assistant Commissioner Neil Basu, Senior National Co-ordinator for Counter Terrorism Policing, said: "We have made a significant arrest in our investigation this morning. Although we are pleased with the progress made, this investigation continues and the threat level remains at critical.
"The public should remain vigilant as our staff, officers and partners continue to work through this complex investigation. We are not, at this time, changing our protective security measures and the steps taken to free up extra armed officers remain in place.
"This arrest will lead to more activity from our officers. For strong investigative reasons we will not give any more details on the man we arrested at this stage."
Detectives from the Met's Counter Terrorism Command are continuing to urge anyone with information about the terrorist attack to contact police.
Thirty people are known to have been injured during the attack in which an improvised explosive device was detonated on a tube train at Parsons Green Underground Station at around 08:20hrs on Friday, 15 September.
So far, detectives have spoken to 45 witnesses and continue to receive information from the public to the confidential anti-terrorist hotline.
The public has sent 77 images and videos to investigators via the UK Police Image Appeal website. Anyone with footage or images from the incident is urged to upload them at www.ukpoliceimageappeal.co.uk where they will be looked at by investigators.
Anyone with information is urged to call the Anti-Terrorist Hotline on 0800 789 321 or, in an emergency, always call 999.
Parsons Green attack
At around 8.20am on 15 September, an improvised bomb partially detonated on a London rush-hour Tube carriage which had stopped at Parsons Green station on the District line. The blast, which injured 29 people, occurred in the south-west of the city, on a train full of commuters including children on their way to school.
Prime Minister Theresa May, acting on the recommendation of the Joint Terrorism Analysis Center, raised the country's threat level from "severe" to "critical", the highest possible level. May said military troops would augment the police presence in a "proportionate and sensible step."
A manhunt began for the perpetrator of the fourth terror attack in the capital this year.
Experts said the bomb, which was hidden in a plastic bucket inside a supermarket bag, only partially exploded. The blast caused no serious injuries.
The Islamic State has claimed responsibility for the attack, although this has not been corroborated.