When you are talking about a thing that has increased, the most usual preposition to use after increase is in .
Don’t say ‘an increase of something’, say an increase in something :
There has been a 2% increase in the rate of unemployment.
Remember: when increase is followed by an amount, the correct preposition is of :
There has been an increase of 2%.
Increase is not usually followed by the adverb ‘up’. Don’t say ‘increase up’, say increase :
The number of homeless people has increased up by 5%.
The number of homeless people has increased by 5%.