They might have been curious.You really have to ask Norwegians.But they do that quite often.One of my friends in Navy once told me P 3 Orions Of Royal Australian Navy used to do surveillance on Indian Navy Ships,especially ships of Russian origin.
WTF???????? so now the Norwegians are playing the game it seems, the Australians used to spy on Indian ships long back, not sure they are doing it right now,however, that spying started when India and US were at odds, after the Bangladesh liberation war, the US and India lacked trust, and the Australians being the ally of US were also skeptic of India,and in 1980's, Indian navy contracted and started buying many ships for its navy of Russian origin, this alarmed the Indonesia, the Indonesians had threatened to attack Indian islands of Andaman to support Pakistan and to divert attention of Indian navy, that's why many ships were bought by the Indian navy and were sent to patrol those regions, and the Australians also used to patrol these waters and used to spy on Indian navy ships, however,we need more ships now, we cannot trust the Indonesians nor the Australians, our tri-service command at Andaman island woefully lacks weapons and infrastructure,we need to develop it fast and quickly, we shouldn't be worried about what the fvck these people think,but i was quiet amused to see Norwegians doing this.