(CNN) Four men have been arrested in Northern Ireland over the murder of journalist Lyra McKee, whose killing last year sparked outrage and calls for talks by rival political factions.

According to a statement from Police Service Northern Ireland, the four were arrested in Londonderry on Tuesday morning under the Terrorism Act.

The anti-terror legislation was used because the New IRA dissident Republican group admitted responsibility for McKee's killing , the police said. In a statement to a local newspaper, the group claimed McKee's death was an accident and apologized.

The men, aged 20, 27, 29 and 52, were taken into custody in Belfast.

McKee was shot dead in April 2019 amid rioting in the Creggan area of the Northern Irish city, which is referred to as Derry by Irish nationalists and as Londonderry by British unionists.

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