The Queen was a “courageous and gracious leader” who contributed to peace and reconciliation in Northern Ireland, a special sitting of the Stormont Assembly has been told.

She was also described as the UK’s “greatest ever monarch” as both unionist and nationalist political leaders paid tribute following her death.

MLAs gathered at Stormont on Monday, where Speaker Alex Maskey opened the session by stating the Queen was held in high regard by many for the significant leadership that she contributed to making political progress in Northern Ireland.

Sinn Fein vice president Michelle O’Neill said the Queen’s life and legacy will be “fondly remembered by many people around the world”.

“Today I wish to record the value and respect I place on the significant contribution Queen Elizabeth made to the advancement of peace and reconciliation between the different traditions on our island, and between Ireland and Britain during the years of the peace process,” she said.

“I recognise that she was a courageous and gracious leader.”

Ms O’Neill added: “She made real efforts, and in good faith, to build relationships with those of us who are Irish, and who share a different political allegiance to herself and her government, and who wish to exercise our right to self-determination based on consent to achieve reunification and a shared island for all.”

The DUP’s Gordon Lyons told the Assembly that no tribute or eulogy could do justice to the life of the Queen.

He said: “Since the news of her death last Thursday, many people in Northern Ireland, across the UK and throughout the world have felt deep sorrow at the passing of someone who, as it has often been said, we will never see the like of again.”

He added: “We have lost our greatest-ever monarch; a leader who was remarkable, not just for the longevity of her reign, impressive though it was, but because she was an exemplar of service, sacrifice and devotion to duty: duty right to the very end.

“That devotion to duty was as evident in Northern Ireland as anywhere else.”

Alliance Party leader Naomi Long said the Queen had shown “unswerving dedication” to duty.

She said: “I think it is a remarkable achievement not just to have served on the throne as the Queen did for such a long period, but to have done so with such unswerving dedication to duty, right to her final hours to have continued in the work to which she was called.

“That, I believe, is a remarkable legacy which she leaves behind.”

UUP leader Doug Beattie told the Assembly that the Queen’s reign spanned “massive political, social and economic change”.

Mr Beattie said he was “deeply saddened” by her loss and that he was experiencing an unexpected sense of grief.

“The Queen remained a constant, creating stability and a national focus,” he added.

“Her Majesty the Queen had a knack of remaining current, accessible and approachable in a changing world.

“Although she would stand with heads of state and prime ministers and presidents, and with other kings and queens, she never lost her common personal touch.”

The SDLP’s Stormont leader Matthew O’Toole said one of the most notable achievements of the Queen was “her extraordinary contribution to reconciliation between Ireland and Britain”.

He added: “The example of Queen Elizabeth was to stretch herself, to be generous and to use the symbolic power of her role not simply to command loyalty but to win respect, warmth and build bridges.”

TUV leader Jim Allister referenced the IRA murder of Lord Mountbatten, the uncle of the Duke of Edinburgh, in 1979.

He said: “Hers was not a life immune from burdens and heartache.

“One such affliction was the wicked murder of the elderly Lord Mountbatten by the IRA.

“Yet she bore it with great fortitude, with generosity, with grace.”

People Before Profit MLA Gerry Carroll did not attend the Stormont session, stating he did not want to take part in “a political ceremony which uncritically supports the institution of monarchy”.

The special Assembly sitting finished with a minute’s silence before MLAs moved into the Great Hall where a book of condolence was opened.

Mr Maskey was the first to sign the book, followed by Ms O’Neill, Edwin Poots of the DUP, Mrs Long, Mr Beattie and Mr O’Toole.

As MLAs signed the book they were flanked by a portrait of the Queen and a photograph of one of her visits to Stormont.

It comes ahead of a visit to Northern Ireland by the new King on Tuesday.

Charles and Camilla will travel to Hillsborough Castle and Belfast for several engagements.

The trip to Northern Ireland follows a visit to Scotland on Monday, with a trip to Wales planned for later in the week.

A significant security operation is under way in the Co Down village of Hillsborough ahead of the royal visit.

People continue to congregate at Hillsborough Castle, the royal residence in Northern Ireland, where a large number of floral tributes have been laid.