How can that be? (Little Upsilon)

"Your country has been invaded by 1 hostile military unit. Attack army units on my territory"

I am in secured mode...how is that possible?

Its probably a supply unit that accidentaly moved over your borders. Ignore it, you cant be attacked in secure.

Pink is right, if you are in a fed or have an empire someone may have placed a depot in your country. Just ignore it.

you are right, it is a supply unit...thx!!!