The Assets Recovery Agency in Northern Ireland is investigating some 250 properties associated with two Manchester-based businessmen as part of a probe into IRA links.
The agency has confirmed that a number of searches had taken place in Manchester involving a £9m property portfolio that had been acquired over a period of time.
It is believed the agency has been investigating the assets of alleged IRA Chief-of-Staff Thomas 'Slab' Murphy.
The move follows a successful application to the High Court in London for search and seizure warrants and a disclosure order.
Commenting on the operation, Minister for Justice, Michael McDowell, said that the ARA and the Criminal Assets Bureau would ensure that those who have derived funds from crime would not enjoy the assets into which they have converted their money.
Northern Secretary Peter Hain said that the ARA would continue with its work to ensure that assets acquired illegally or criminally would be tracked down and seized.
Meanwhile, Sinn Féin President Gerry Adams has criticised the timing of the operation, saying the announcement had been politically motivated to coincide with today's talks at Downing Street.
Mr Hain denied this, saying the activities of the agencies were independent of any political discussions.
The Manchester operation was welcomed by DUP leader Ian Paisley who was also at Downing Street for political talks today.
He said the operation should have started earlier to deal with what he termed 'IRA racketeering' and that those involved 'should be removed from the society they had cursed for so long'.
