He was Northern Ireland’s former Deputy First Minister and one-time IRA commander.

Northern Ireland's former Deputy First Minister and one-time IRA commander Martin McGuinness has died aged 66, his Irish nationalist party Sinn Fein said on Tuesday.

Mr. McGuinness had resigned from politics in January, citing a serious illness and a breakdown in relations with the rival Democratic Unionist Party.

"It is with deep regret and sadness that we have learnt of the death of our friend and comrade Martin McGuinness who passed away in Derry during the night," Sinn Fein said in a statement.

The BBC said he had died of a rare heart condition.

Sinn Fein refused to appoint a replacement for Mr. McGuinness in January due to a row with the DUP, its partner in a power-sharing government set up to bring peace to the Province.

That triggered local elections in which Sinn Fein made major gains against the DUP and the two parties are currently deadlocked, meaning that the British government could impose direct rule of Northern Ireland from London.

Ten years ago in May, Mr. McGuinness had made history by entering a government with his once bitter foe, Ian Paisley of the DUP.

The decision to share power was a key part of the peace process in Northern Ireland, which endured three decades of violence in which more than 3,500 people died.

Mr. McGuinness was a commander in the IRA paramilitary group that fought for the Province to leave Britain and join the Republic of Ireland to the south.

In a memorable gesture that would once have been unimaginable, he shook hands with Queen Elizabeth II during her visit to Belfast in 2012.