British anti-terror police arrested seven people across England and Wales in a series of raids in the early hours of Tuesday morning.

The Metropolitan Police Service (MPS) operation, which also involves Homeland Security Investigations in America, is investigating a network suspected of illegally exporting the stimulant khat, which is legal in Britain, to the United States and Canada where it is a controlled substance.

The seven, six men and one woman, were arrested at four separate residential addresses in London, Coventry, and the Welsh capital of Cardiff at approximately 6 a.m. on suspicion of being concerned in the funding of a terrorist organisation, and laundering the proceeds of crime for that purpose.

The seven arrested were a woman, 45, and a man, 49, in Croydon; a man aged 47 and another man aged 30 in Brent, a district of northern London; a man aged 45 and another man aged 42 in Coventry; a man aged 40 in Cardiff.

Khat is a leafy plant which is often chewed for its narcotic effect. It is used among the Somali community in Britain, and Somalia is the home of an al-Qaeda linked organization al Shabaab.

The co-ordinated operation is led by the MPS's Counter Terrorism Command, with assistance from the Counter Terrorism network, the UK Border Agency and regional police forces.

The arrests were a part of a pre-planned, intelligence-led operation, into suspected fundraising for terrorism overseas.

A further eight search warrants were executed at seven residential addresses in London, the south coast town of Worthing, and Coventry, and a business premises in Coventry.

The searches are ongoing and there have been no arrests at these premises, police said.