The IRA followed up the announcement with its own terse statement: "The IRA leadership can now confirm that the process of putting arms beyond use has been completed."
The material included ammunition, rifles, machine-guns, mortars, missiles, handguns and explosives, said John de Chastelain, a retired Canadian general who since 1997 has led efforts to disarm the outlawed IRA.
"We are satisfied that the arms decommissioning represents the totality of the IRA's arsenal," de Chastelain told a news conference.
All the weapons were rendered "permanently inaccessible or permanently unusable," said de Chastelain, who began working on the process eight years ago.
The IRA permitted two independent witnesses — a Methodist minister and a Roman Catholic priest close to Sinn Fein leader Gerry Adams — to view the secret disarmament work conducted by officials from Canada, Finland and the United States.
De Chastelain, who in recent weeks has been in secret locations overseeing the weapons destruction, earlier in the day gave representatives of the British and Irish governments a confidential report on his work.
Questioned by reporters, de Chastelain said he could not be absolutely certain that every IRA weapon had been disposed of, but he said he believed the IRA was sincere in saying it had handed over the whole arsenal. He also said the amount was consistent with police and army estimates of the IRA's holdings.
The breakthrough should smash the biggest stumbling block in Northern Ireland's peace process since Britain opened negotiations with Sinn Fein, the IRA-linked party, in 1994.
"It has been a very significant journey, a roller coaster at times," said senior Sinn Fein official Mitchel McLaughlin. He said he hoped IRA disarmament would prove "a defining and, hopefully, a liberating moment for the process" that would promote "confidence and generosity in response from our opponents."