POST Office workers at a handful of larger branches in the north will go on strike on Saturday in a dispute over pay.
Members of the Communication Workers Union (CWU) at Crown Post Offices, which includes half a dozen branches in Northern Ireland, will walk out on Saturday.
The union said staff in administration and supply chain networks will then walk out Monday, which could affect cash collections and deliveries at sub-post offices.
The strikes follow industrial action earlier this month.
Crown Post Offices are directly managed by Post Office Limited. The list includes Belfast city centre, Derry’s Custom House Street as well as branches in Coleraine, Antrim, Newtownards and Bangor.
The union said Post Office management is insisting on a pay freeze for 2021-22 and a "marginally improved" pay offer for 2022.
CWU assistant secretary Andy Furey said: "Our members do not want to be in this situation, but they won't accept humiliation either.
"Our members worked hard to deliver an excellent annual profit for the company - affordability isn't management's problem here.
"Frankly, their degrading excuse for an offer has only hardened members, who won't tolerate a collapse in their living standards.
"We thank the public for their understanding and support, and we urge Post Office to get round the table and thrash out a real settlement that treats key worker heroes with the respect they deserve."
Around 3,500 union members are involved in the UK wide dispute.
A Post Office spokesperson said: "We want to assure our customers that the vast majority of our branches are unaffected by CWU strike action on Saturday.
"There are 114 branches, typically in city centres, that are directly managed by Post Office.
"Over two-thirds would normally only be open between 9am and 12.30pm on a Saturday. We apologise to any customers who are inconvenienced by a closure."
