BERGEN - Norwegian oil company Hydro is celebrating their 100-year anniversary and "Per Gessle & band" have accepted an invitation to play for the staff in the northern town of Bergen on September 3.

  Hydro's celebration starts today in Oslo with Norwegian popgroup a-ha giving a free concert in Frogner Park. a-ha, who recently performed at the Live 8 concert in Berlin, will premiere some of the music on their latest album. The group will also play an already sold-out gig at New York City’s Irving Plaza on September 12, their first US concert since 1986 and almost exactly 20 years after the hit "Take on Me" soared to the top of the charts worldwide.

  Per tells The Daily Roxette that he will play Bergen and Stockholm in September to keep his band Mazarinerna in good shape.

  This isn't the first time Per has played company gigs, Roxette played for the OM group a few years back, beer giant Carlsberg has had a visit as well, and now last summer Swedish operator Tele 2 had Gyllene Tider visit them.

Elisabeth Mathisen contributed to this article.

• Hydro