G4S, the firm behind the Olympic security fiasco, is to provide support at the G8 Summit in Northern Ireland this summer.

The firm, which suffered a multimillion-pound loss after failing to provide all its 10,400 contracted guards to the Olympics last year, will supply 450 staff to the event at Lough Erne golf resort on June 17 and 18 when leaders of the world's eight wealthiest countries arrive.

The announcement came as Northern Ireland Secretary Theresa Villiers revealed additional military personnel and thousands of police officers from across Britain will be drafted into help the PSNI (Police Service of Northern Ireland).

On G4S's contract win, Ms Villiers said lessons had been learned and said the UK Foreign Office was confident the firm could deliver.

She did not say how many extra troops would be deployed to Co Fermanagh but said military assistance would be used to back up the police. Army helicopters will fly world leaders and their entourages to and from the event outside Enniskillen.

Meanwhile, PSNI Chief Constable Matt Baggott said he expected thousands of protesters to descend on Northern Ireland during the summit. He said: "We are expecting demonstrations in Belfast and we are expecting some in Enniskillen as well."

G4S said staff will provide stewarding, monitoring of site perimeters and securing access to venues. The firm has previously supported a number of summits, including the 2005 G8 in Gleneagles and the G20 in London.

Eric Alexander, managing director of G4S Events, said: "We are delighted to have been awarded this contract and be given the opportunity to use our proven expertise to help the PSNI secure this extremely high-profile event."

G4S was left nursing losses of £88 million after it failed to provide all of its contracted employees to the Olympics.

Northern Ireland-based company Event Sec will also be used to secure perimeters and to carry out searches.

A total of 3600 police officers from forces in England, Scotland and Wales are being drafted in to bolster the 7500 from the PSNI.