The FBI has arrested 10 alleged Russian spies and broken up a “long term, deep cover” network of agents.

They were allegedly part of an operation where agents posed as ordinary citizens, some living together as couples for years.

They are accused of conspiracy to act as unlawful agents of a foreign government, a crime which carries up to five years in prison.

Nine of them also face a charge of conspiracy to launder money, which carries a 20-year prison sentence.

An 11th suspect remains at large, according to the US justice department.

The arrests were made in Arlington, Virginia – close to the Pentagon and CIA headquarters – and in New York, Boston and New Jersey.

One of the detained couples lives on the west coast, in Seattle. The justice department said one other alleged spy, who is accused of delivering payments to members of the ring, is still being sought.