The event took place in the capital city's City Hall and the Crown Prince was joined by other notable guests, his wife Crown Princess Mette-Marit and county councillor Valgerd Svarstad Haugland.
Nearly 400 new Norwegian citizens were welcomed during the ceremony.
The citizenship ceremonies have been organized and run since 2006. They are for for every new Norwegian national above 12 years of age. Taking part in the event is completely voluntary.
The ceremony on Sunday was for Oslo and Akershus citizens, and peopel with origins from 76 different countries were wished welcome to their new country.
The new citizens swear the following oath of loyalty during the ceremony: “As a Norwegian citizen, I pledge loyalty to my country Norway and to the Norwegian society, and I support democracy and human rights and will respect the laws of the land.”