Martin McGuinness, a former Irish Republican Army commander who was deputy first minister of Northern Ireland for a decade, has died aged 66, his party, Sinn Fein, announced on Tuesday.

A key figure throughout five decades of conflict and peace in the UK province, McGuinness had announced on January 19 that he was bowing out of politics and would not lead his nationalist party into elections in March.

He said illness and a political crisis triggered by his own resignation as deputy first minister earlier in January had led to him to step down several months earlier than planned.

Shortly after his retirement, Sinn Fein achieved a major electoral breakthrough in elections to Northern Ireland's assembly, coming within one seat of the Democratic Unionist Party and depriving the pro-British political camp of an overall majority for the first time since the partition of Ireland in 1921.