Six men and one woman were arrested by anti-terror police from four separate residential addresses in London, Coventry, and Wales capital Cardiff at 6 a.m., Xinhua reported.
The operation handled by the Metropolitan Police Service (MPS), also involves the US Homeland Security department.
The seven include a 45-year-old woman and a 49-year-old man in Croydon, a 47-year-old and a 30-year-old in Brent district of northern London, a 45-year-old and a 42-year-old in Coventry and a 40-year-old man in Cardiff.
Their nationalities were not disclosed.
The gang is suspected of illegally exporting a stimulant called “khat”, a leafy plant chewed for its narcotic effect. It is used among the Somali community in Britain.
The substance, which is legal in Britain, was allegedly being sent to the US and Canada, where it is a controlled substance.
The joint operation was carried out by the MPS’s Counter Terrorism Command, with assistance from the Counter Terrorism network, the UK Border Agency and regional police forces.