Martin McGuinness, a former Irish Republican Army commander and deputy first minister of Northern Ireland who was a key figure throughout five decades of conflict and peace, has died at 66, his party, Sinn Fein, said on Tuesday.

McGuinness, whose journey from street fighter to peacemaker began in the 1970s during Northern Ireland's "troubles," had bowed out of politics several months earlier than planned in January due to an undisclosed illness.

"Throughout his life Martin showed great determination, dignity and humility, and it was no different during his short illness," Sinn Fein President Gerry Adams said in a statement.