Northern Ireland's new First Minister and Deputy First Minister have responded to the news that King Charles has a form of cancer.

“I am very sorry to hear of King Charles illness and I want to wish him well for his treatment and a full and speedy recovery,” O’Neill said in a post on X on Monday afternoon, not long after the news emerged.

I am very sorry to hear of King Charles illness and I want to wish him well for his treatment and a full and speedy recovery.

— Michelle O’Neill (@moneillsf) February 5, 2024

Deputy First Minister Emma Little-Pengelly also said: “I would like to wish His Majesty, King Charles all the the very best for his treatment.

"I, like many people throughout Northern Ireland,  will keep him and his family in my prayers.”

On Monday, Buckingham Palace said in a statement: “During The King's recent hospital procedure for benign prostate enlargement, a separate issue of concern was noted. Subsequent diagnostic tests have identified a form of cancer.

“His Majesty has today commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties.

“Throughout this period, His Majesty will continue to undertake State business and official paperwork as usual.

“The King is grateful to his medical team for their swift intervention, which was made possible thanks to his recent hospital procedure. He remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible.”

A statement from Buckingham Palace: https://t.co/zmYuaWBKw6

? Samir Hussein pic.twitter.com/xypBLHHQJb

— The Royal Family (@RoyalFamily) February 5, 2024

The statement from Buckingham Palace comes on the same day the newly formed Northern Ireland Executive held its first meeting since power-sharing was restored over the weekend after nearly two years of collapse.

First meeting of the new Executive was held today in Stormont Castle. pic.twitter.com/64FRRFwDWB

— NI Executive (@niexecutive) February 5, 2024

Charles ascended the throne in the wake of the death of his mother, Queen Elizabeth, in September 2022.

After the Queen's death, O'Neill, as well as Sir Jeffrey Donaldson of the DUP, met with Charles at Hillsborough Castle in Co Down.

"So sorry for your loss, so sorry," O'Neill told Charles, shaking his hand.

"You're very kind," Charles replied. "And thank you so much for your incredibly kind things that you said about my mother."

O'Neill said: "Well, she played a great role here in terms of reconciliation and building our peace. So, it's the end of an era, for sure."

"I know, to say the least," Charles said, adding: "And what is so sad is you can never read your obituaries and all the nice things people say about you."

O'Neill agreed: "We don't say enough about people whenever they're alive, for sure."

Charles continued: "Anyway, it's very good to see you again, because I haven't seen you for a bit?"

"Yes, I know," O'Neill said. "A few years. Cork, I think, was the last time we met."

Charles said: "What are you now? The biggest party, are you?"

"We are indeed," O'Neill said, "we are indeed."

► VIDEO: "What are you now... the biggest party, are you?" - when Britain's King Charles met Sinn Féin's Michelle O'Neill pic.twitter.com/ghNtt2vAbH

— Irish Times Video (@irishtimesvideo) September 14, 2022

Later, O'Neill accepted an invitation to attend the coronation of King Charles in May 2023.

Today I will attend the Coronation of King Charles III as First Minister Designate. My determination is to keep moving forward, and to represent the whole community. The political landscape across our island is changing. My focus is on building a shared future for all.

— Michelle O’Neill (@moneillsf) May 6, 2023

Not long after the coronation, Charles and his wife Camilla made a 'surprise' two-day visit to Northern Ireland.