Police are investigating claims private detectives working for Rupert Murdoch's British newspaper arm hacked into the computer of a Northern Ireland minister, potentially compromising highly sensitive information, the Guardian daily reported on Tuesday.

The newspaper said the new allegations suggested that malpractice at News International, News Corp's British arm which is at the centre of a phone-hacking scandal, was far more serious than thought.

The Metropolitan Police said it would not provide a running commentary on its investigations. News International said it had no comment on the allegations.

According to the Guardian report, the computers of Peter Hain, who was Northern Ireland Secretary in 2005-2007, as well as senior civil servants and intelligence agents were targeted by private eyes with connections to News International.

Hain has not confirmed the Guardian story but his spokesman said in an emailed statement: These are matters of national security and are subject to a police investigation so it would be inappropriate to comment.

A source at News International said it had not been confirmed that any of the alleged computer-hacking involved its employees.

Hain was Northern Ireland Secretary during a significant period for the province when Irish Republican Army (IRA) guerrillas ended their armed fight against British rule after a 30-year campaign and decommissioned their weapons.

The phone-hacking scandal has engulfed much of the British establishment since it rose to prominence in July when it was revealed the News of the World had hacked the phone of a missing schoolgirl who was later found murdered.

Prime Minister David Cameron's former media chief Andy Coulson, previously an editor at the tabloid when hacking occurred, and a number of senior News International figures have lost their jobs and been arrested.

Meanwhile, two of London's police top officers were also forced to quit their jobs over the scandal.

Staff from News International are already at the centre of a phone-hacking furore that forced the closure of one of its papers, the 168-year-old News of the World tabloid, and more than a dozen have been arrested as part of a police probe.

The scandal also prompted Cameron to order a public inquiry into press standards which has thrown up further damaging revelations and allegations.

On Monday, Ian Hurst, a former British army intelligence officer who served for a decade in Northern Ireland until 1991, told the inquiry that his computer had been hacked by private investigators working for the News of the World in 2006.

He said he believed the paper was looking for details about an informant from the IRA.

Last week, detectives working on the computer-hacking allegations made their first arrest when a 52-year-old man was questioned.

(Editing by Maria Golovnina)