A statement from the Police Service of Northern Ireland said:
Detectives from the PSNI's Serious Crime Branch, with assistance from officers in Cumbria Constabulary and the North West Counter Terrorism Unit, are conducting a number of searches in Northern Ireland and north west England.
The search activity is in connection with the wider investigation into the murder of PSNI Constable Ronan Kerr in April 2011 and linked incidents.
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