The Sinn Fein Mid-Ulster MP, one of a stream of visitors to Lammy Crescent, spent time at nearby St Conor's Primary School - where two of the dead children were pupils - and spoke to teachers and other staff.

He also spoke with and praised the teams of firefighters, many of whom had worked through the night at the collapsed home, which was last night being described as a murder scene by the PSNI.

"I am deeply saddened at the scale of this loss of life and I am told that this is the largest loss of life in a house fire in the history of the state," he said.

"I obviously want to express my deepest sympathy to the family and to the whole of the Lammy community.

"I was very pleased with the firefighters, some of whom have had no sleep whatsoever. We are forever in their debt."

He said that the work of the emergency services at the scene of the blaze was in stark comparison to how some of their personnel are treated on the streets.

The minister pointed to attacks on the Fire Service and the shooting of two police officers in Londonderry and Dungannon in the past week.

"These people should come and look at the work being done here in Omagh - they would soon change their minds."

Mr McGuinness added: "All of us are heartbroken and we should all dedicate our prayers to the McElhill and McGovern families, the community and the emergency services."

He said that the people of Lammy will "never forget" what had happened, adding: "This will stay with them for the rest of their lives. "

Earlier Michelle Gildernew, Pat Doherty and Conor Murphy also visited the scene.