London (CNN) A group calling itself the IRA has claimed responsibility for a series of improvised explosive devices that were sent to locations in London and Glasgow last week, the Metropolitan Police and Police Scotland said Tuesday.

The forces said in a statement that they are "aware of the claim of responsibility for the devices that were received at three buildings" in the UK capital and at the University of Glasgow on March 5 and 6. "The claim was allegedly made on behalf of the 'IRA,'" they added.

The claim of responsibility was received by the Northern Irish newspaper The Irish News on Monday and a recognized codeword was used, said the statement.

A package sent to Heathrow Airport, which ignited

As the devices "bore similarities" to past packages "linked to dissident groups associated with Northern-Ireland related terrorism," the police said that "officers were already looking at this as a line of enquiry."

The group claims to have sent five devices, of which four have currently been recovered by police.

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