Rudd made the statement after British police arrested two suspects in connection of the explosion in a packed rush-hour carriage on Friday at Parsons Green subway station.
"The police have made very good progress".
British officials have lowered the country's official terrorist threat level from "critical" to "severe" following the arrest of a second man in the London subway bombing.
"Severe still means that an attack is highly likely so I would urge everybody to continue to be vigilant but not alarmed".
An 18-year-old man was detained in the departure lounge of Dover port, in Kent, and a 21-year-old man was held at a house in Hounslow, west London.
One or two residents who spent the night elsewhere have been returning to the road to collect belongings - they are being allowed to do so only with a police escort to and from their home.
The second arrest comes after an 18-year-old - the youngest to be arrested over a terror attack in the United Kingdom - was quizzed by cops after he was seized in Dover.
Une abominable tentative d'escroquerie — Disparition de Maëlys
Le drame de la disparition de Maëlys , toujours introuvable depuis le 27 août en Isère, n'arrête pas les escrocs. Pour l'instant, on ne sait pas s'il a été identifié par les gendarmes, ni s'il a été interpellé.
The Home Secretary has said it appears the bomber was not a lone wolf but it is "too early to reach any final conclusions on that".
She told the BBC's Andrew Marr Show: "This has been a year like no other - we've seen five serious attacks and six that were foiled by the police". "We have no evidence to suggest that yet".
Two men are now in custody for possible roles in the bombing attack on a rush-hour subway train Friday that injured 29 people in London.
Police are continuing to search a foster home in Sunbury-on-Thames, Surrey, in connection with the teenager's arrest on Saturday.
A friend, Alison Griffiths, said they are "great pillars of the community" who have taken in several hundred children in the last 40 years.
Counter-terrorism officers are leading the investigation supported by MI5.
The first suspect was arrested at around 7.50am, in the port which is the busiest ferry hub in Europe and serves as a commercial gateway to the French coast, including Calais and Dunkirk.
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