LONDON (Reuters) - A man from Northern Ireland was arrested in Britain on Monday in connection with the death of Northern Ireland policeman Ronan Kerr, who was killed in April last year when a bomb exploded under his car, the Police Service of Northern Ireland said.

The 22-year-old man, from Omagh in County Tyrone, was detained in Milton Keynes, England, as police widened their investigation to northwest England. Police said they were conducting searches in Northern Ireland and northwest England.

Kerr, 25, was the first policeman killed in the British-controlled province for two years. A Catholic, Kerr was a new recruit and a symbol of Northern Ireland's new police service, which before the peace deal was predominantly made up of Protestants and viewed with skepticism by many Catholics.

The arrest of the suspect, who was not named, was made by the North West Counter Terrorism Unit at the request of PSNI Serious Crime Branch detectives, according to the PSNI.

A prison officer, David Black, was shot and killed in his car earlier this month, and a group of militant Irish nationalists claimed responsibility.

International monitors confirmed in 2005 that the Provisional Irish Republican Army had given up all its weapons, but dissidents disenchanted with the peace process, which largely ended three decades of violence in which over 3,600 people died, have increased violent activity in recent years.

Earlier this year, militant nationalist groups in Northern Ireland united under the banner of the so-called New IRA.

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(Reporting by Stephen Mangan; Editing by Jackie Frank)