A group using the name of the Irish Republican Army has claimed it sent a series of suspicious packages to British military recruitment centres, British police have said.
Police said on Monday that the claim carried a "recognised codeword" used by the paramilitary group, which officially ended its armed campaign in 2005.
"The claim was received on Saturday, 15 February by a Northern Irish media outlet using a recognised codeword. The claim was allegedly made on behalf of the 'IRA'," a statement from London's Metropolitan Police said.
Seven crude devices were mailed to armed forces careers offices in southeast England last week. None went off.
British government officials said at the time that the devices had the hallmarks of Northern Irish groups.
The Belfast-based newspaper, The Irish News, reported receiving the statement.
It said: "The IRA claims responsibility for the explosive devices that were sent to British armed forces recruitment centres in England. Attacks will continue when and where the IRA see fit."
Irish groups used recognised codewords to warn of impending attacks or claiming responsibility for them.
The IRA ended its armed campaign in 2005, pledging it would use purely peaceful and democratic means towards achieving its goal of uniting Ireland.
However, small, dissident splinter groups remain wedded to violence against British state institutions.
Dissident republican paramilitary groups reject a peace process in Northern Ireland and continue to carry out attacks, with the intention of destabilising the province and the power-sharing arrangements between the Protestant and Catholic communities.
These splinter groups include the Continuity IRA and the New IRA, which incorporates the better-known Real IRA.
The New IRA was blamed for letter bombs sent in October to Britain's Northern Ireland minister and the province's police chief.
About 3,500 people died in Northern Ireland's three decades of violence between those loyal to the British crown, and republicans. A 1998 peace agreement largely ended the conflict.
The IRA's political wing, Sinn Fein, is now part of the power-sharing government in Belfast, formed of Catholic and Protestant parties.