I have noticed this in both print and on-line news
Here are a few recent examples:
‘Attackers kill Nigeria Christians’
‘Japan whalers given ....’
‘Chad troops to fight .....’
‘Kenya army rampage’
‘Norway minister’s EU exit warning’
'Canada's new plastic banknotes feature Norway maple leaves instead of the Canadian sugar maple leaf.'(Why Canadian and not Norwegian???)
‘Paraguay peasant leader shot dead’
Curiously, on the same webpage and immediately below
the headline above, it had:
‘Slovenian ex-PM wins presidency’ ???!!
So why use ‘Slovenian’ if you don’t use ‘Nigerian’ or ‘Kenyan’? Where’s the justification or reasoning?
‘Nigeria’ and ‘Kenya’ are proper nouns; they are not adjectives!
Are we seeing ‘Australia beach closed due to shark attack’ or ‘Britain man accused of ...’? Well, not yet and hopefully never. Come on media editors, do your jobs and get back to proper English!