DUBLIN, Ireland — A special police detective unit will reopen investigations into 1,800 killings from Northern Ireland's bloody past, Britain and the province's police chief announced Tuesday.

The decision follows years of complaints from victims' relatives that British authorities had given up on solving many killings, particularly those committed by Northern Ireland's rival paramilitary groups.

Britain's governor for Northern Ireland, Paul Murphy, said the government had committed the equivalent of $57 million to form a special team of detectives led by officers from outside Northern Ireland.

Murphy estimated the effort to identify those responsible for about 1,800 killings from 1969 to 1998 — accounting for more than half of the death toll from Northern Ireland's conflict — would run for six years.

Under the 1998 peace accord for Northern Ireland, anybody linked to a truce-observing group who is convicted of a politically motivated killing is eligible for speedy parole. This makes reopening most murder investigations in Northern Ireland more a question of revealing the truth than achieving justice.

Most parties welcomed the decision, even though Murphy said he did not expect many prosecutions or convictions to come from the work, in part because of little evidence. In some cases, detectives are expected to use modern DNA analysis on decades-old evidence to identify the killers.

Irwin Montgomery, chairman of the Northern Ireland Police Federation, said he hoped that new investigations would "bring closure" to the families of 211 officers whose killings — largely committed by the outlawed Irish Republican Army — remain unsolved.

A moderate Catholic politician, Alex Attwood, said the new investigation must also address the fact that, in many cases involving the killing of Catholics, relatives believe the original investigations by Northern Ireland's mostly Protestant police were inadequate.

But he said the effort to reopen investigations offered "remarkable contrast" to the policies of Northern Ireland's underground groups, chiefly the IRA and the Ulster Defense Association, the major anti-Catholic group.

Those groups, Attwood said, "refuse to account for their actions and insult the memory of many families and many in the community by refusing to acknowledge killings as murder and widespread human-rights abuses as crimes."