Martin McGuinness has challenged political rivals making claims about Sinn Fein links to criminality to "put up or shut up".

As cross-party talks got under way in Belfast to save the power sharing administration amid a crisis over an IRA-linked murder, the Sinn Fein Deputy First Minister made a fiery defence of his party's commitment to peace.

"I am not putting up with this nonsense any more," he said.

However, Democratic Unionist leader Peter Robinson, who took part in the talks less than 24 hours on from being discharged from hospital after suffering a bad reaction to heart medication, said it was vital the process examined paramilitary links with "political parties in government".

The devolved Assembly has been thrown into disarray following the murder of ex-IRA man Kevin McGuigan last month.

The 53-year-old father of nine was shot dead in Belfast in a suspected revenge attack for the murder of former IRA commander Gerard "Jock" Davison, 47, three months earlier. Detectives believe some of Mr Davison's associates suspected Mr McGuigan of involvement in his shooting.

A police assessment that individual members of the IRA were involved in the McGuigan murder prompted unionists to remove all ministers but one from the coalition Executive, claiming Sinn Fein was inextricably linked to the supposedly defunct republican terror group.

Mr McGuinness had strong words for his party's accusers as he emerged from the first round table talks session with the four other Executive parties and the British and Irish governments at Stormont House.

"Some parties within these negotiations are attempting to give the impression that there's linkage between a party in government - what they mean by that is Sinn Fein - and criminality," he said.

"During the course of this morning's engagement I took those people to task. I told them if anybody has any information whatsoever about any party in government being involved in criminality that they should put it up on the table and, more importantly, they should put it to the PSNI (Police Service of Northern Ireland).

"In other words I told them it is now time for them to put up or shut up."

Mr McGuinness name-checked the Ulster Unionists and SDLP in the course of his comments.

"I am not going to be accused by others who are trying to besmirch the name of my party," he said.

Last week, the DUP and UUP said the issue of paramilitary activity was crucial to their participation in any talks process.

Mr Robinson said he was feeling fine, after briefly attending hospital following a reaction he suffered to his medication.