The low-cost carrier will offer services between Reykjavik and the Irish and UK cities over selected periods next summer.
Customers based in Scotland will benefit from twice-weekly flights operating every Monday and Friday between June 14 and August 30 next year, with lead-in fares of £101 each way.
The Belfast service will run via Edinburgh, with similar prices, while the weekly Dublin flights (every Tuesday) will run between June 10 and August 29, with one-way fares from £98.
There are currently no direct flights from these destinations to Rekjavik, and Iceland Express says it will offer connecting services onto its US routes, with a free stopover in Rekjavik.
The carrier recently announced it will fly to Chicago and Boston next summer, as well as increasing its New York operations to a daily service (see online news August 25).
Lead-in connecting fares start from £205 one-way between Dublin/Edinburgh and the US, and £220 from Belfast.
Iceland Express flies from both London Stansted and Gatwick to Rekjavik, while rival Icelandair operates from London Heathrow, Manchester and Glasgow.
For more information visit icelandexpress.com.
Report by Mark Caswell