The rail union’s general secretary Mick Cash said the strikes will go ahead on Friday, September 1 and Monday, September 4, in a long-running dispute over staffing and driver-only trains.
The announcement comes following a meeting earlier today between Mr Cash and officials at Arriva Rail North - which operates the Northern franchise.
Further RMT strikes have been called at Southern Rail on the same dates and at Merseyrail on September 1,3 and 4.
The union has accused all three companies, and the Government, of pressing ahead with controversial plans to extend driver-only operation.
In a statement released after the talks with Arriva Rail North, Mr Cash accused the company of “intransigence”.
“The responsibility for the inevitable disruption lies wholly with the company,” the union leader said.
“We are angry and frustrated that Arriva continue to fail to face up to the facts and also continue to ignore a perfectly reasonable union proposal to invite the DfT (Department for Transport) to join us in round-table talks aimed at finding a solution.
“The public, who support RMT’s campaign for a guarantee of a guard on their trains, will be appalled that Arriva Rail North have failed yet again to offer any kind of progress whatsoever in the talks and have instead opted to try and bulldoze through their plans regardless.”
The union continues to remain available for meaningful discussions with the company in order to seek a satisfactory resolution to the on-going dispute, Mr Cash added.