No, this is not an alien structure it is another weird church in Iceland.
I ve found two different versions about this church:
Version #1: It was built in 1990 and the architect is J n Haraldssyni
Version #2: The church in Stykkish lmskirkja was built in 1879. The new church was than built in 1980. The church has drawn much of detention by its look from the sea and from land. In 1939 Fransiskusystur (nuns) built a monestry, school and the church. They also built a hospital witch is still in use.