Norway will become the third country to donate F-16 fighter jets to Kyiv to bolster its Soviet-era air force, three Norwegian media reported Thursday, without citing any sources.

Neither the number of planes nor the delivery date were announced, as Ukraine pursues a grinding counteroffensive against Russian forces in the east.

Contacted by AFP, a spokeswoman for Norway's defence minister could "neither confirm nor deny" the media reports.

The reports came as Norwegian Prime Minister Jonas Gahr Store made a surprise visit to Kyiv on Thursday, which was also Ukraine's Independence Day.

Of the 57 F-16s Norway officially has up for sale, 32 have already been sold to Romania and 12 have been sold to US group Draken International, but have not yet been delivered.

If the reports from broadcasters NRK and TV2 and newspaper Aftenposten are confirmed, Norway would become the third country after Denmark and the Netherlands to give F-16s to Ukraine.