MOSCOW – A former paratrooper attempting a record-breaking 36,000-mile trek around the world has been arrested by Russian border guards after becoming the first Briton to walk across the Bering Strait.

Karl Bushby, 36, from Hull, and his fellow adventurer, Dimitri Kieffer – who lost a finger from frostbite – were being interrogated by the security service FSB, officials in the remote Chukotka region of Siberia said.

They were detained on April 1 after a hazardous two-week hike across the 58 miles of partially frozen sea that separates the North American landmass from Asia.

Although they had Russian visas, they were arrested for failing to enter the country through an official border crossing. They aroused further suspicion because they were carrying satellite and navigation technology and a revolver. The guards were doubtful of their explanation that the gun was to scare off polar bears. British diplomats in Moscow said they had been in touch with officials in Chukotka, nine time zones to the east, and were hoping to resolve the situation soon.

An embassy spokesman said the men appeared to have been confined in a hotel rather than prison.

Chukotka’s governor is the owner of Chelsea FC, Roman Abramovich, although he spends little time there. The local FSB answers directly to Moscow.

Mr. Bushby, who began his trek at the southern tip of Chile seven years ago, had started the 200-mile walk to the town of Provideniya, where he hoped to register in accordance with the law, when he and Mr. Kieffer were found by the puzzled guards.

The men’s Web sites said they had been expecting trouble with the authorities.

Mr. Bushby’s father, Keith, who lives in Hereford, said: “The authorities could be difficult about it and say they are spies – although not many spies have a Web site giving the full details of when they will be arriving.”