'Yet' adds emphasis to the phrase 'another city'. If the text simply said 'another city', we might understand this was only the second city to be affected. But the use of the term 'yet another' tells us that a number of other cities have already been affected, and the addition of this city makes that number even larger.
The word 'another' can just be 1 + 1, or 2 + 1 - we don't know.
The words 'yet another' mean [ an already large number] + 1.
So, for example, if you say 'We've run out of money yet again', you know that this has already happened a number of times before. This isn't only the second time that we've run out of money - it could be the fourth or tenth time.