they breed in the northern danube delta since about 10 years and are commonly seen there, esp. near coast.
but hey, this bird doesn't look like a pallas's. i have darkened it a bit and the bases of primaries still should look white in ichtyaetus - they don't.
the mirrors are not round like in 2nd cycle pallas's, and in 3rd cycle they usually are adult looking! head pattern is disturbing. it is not like in pallas's but i really wonder if it could be a 3rd cycle hybrid pallas's x caspian. as said, they both breed on a small islet off the northern danube delta, partially in ukraine, partially in romania. i don't know of any documented hybrid of these two yet...
otherwise it could of course be a very odd 3rd cycle caspian gull. but i don't think so.