All of these phrases show that your trip is for business rather than leisure. The simplest phrase I think is to just say that you are on a business trip.
These two sentences can be used interchangeably to have the same meaning. The main difference between the two phrases is that one is using the phrase, "business trip," to describe the purpose of the trip whereas the other one is describe the reason why you are, "here," or currently at this specific location.
Unfortunately I cannot enjoy the sights, because I am here on business.
The proper way to say that you are visiting a place because you are working is "I am on a business trip." or "Unfortunately I cannot enjoy the sights, because I am here on business." The phrase that captures the proper form is "on business."
If you are just casually conversing with someone you can just say "I am here working." It is short and simple and is perfect for any casual conversation.
I am here for business only, so I can't go sightseeing
This is a business trip. I am unable to enjoy the famous sights of the city
Unfortunately, sometimes when we are travelling, we are travelling for business only, not pleasure. We would love to see the famous parts of the city we are visiting but our timetable doesn't permit this. Not only this but it is not part of our agenda.
We can use either of these two sentences to describe that we are visiting just for business.
I am here on work.
I am here for work.
I am here on a business trip.
When you want to explain that you are visiting somewhere on business and not as a sightseer, you can use one of these three sentences and everyone will understand. Personally, I would go for the first one. Pick one, use it, pick another, give it ago, and see what happens. Good luck with them and enjoy it.
I hope this helps.
Have a great day.
Will
1. I'm travelling for business.
When you are travelling for business then it means that
this is not a leisure trip which includes sight-seeing. The
length or duration of your trip is intended for you to
conduct business meetings or visit business sites and not to
have fun.
2. This is solely a business trip.
"Solely" means only. This means that you have no intention
or even the time to visit popular tourist spots. Your entire trip
will be dedicated to business meetings.
To say that you are in a place for working, native speakers commonly use are:
-I'm here on business.
'on business' means that the reason you are in a place is to work.
-I'm here for work.
'for work' is the same definition as above.
-I'm working here.
When abroad, when someone asks you if you are here for sightseeing, you want to say that you are here for business/work. In that case, any of the above suggestions will be fine.