Both present and past tense are possible. I tend to prefer the present.
"Backshifting" is the tendency when reporting speech to change the tense to past tense. Sometimes this makes sense:
Hamza said "I'm working in a cafe".
Hamza said that he was working in a cafe.
But it is not required, and not backshifting can emphasize that the person reporting believes something is still true.
Hamza said that he's working in a cafe. It must be a new job.
For "facts" there is no need to make this emphasis, as the fact isn't going to change, so
Hamza said that London is the biggest city.
Hamza said that London was the biggest city.
would mean the same. Perhaps the second could be used if you want to doubt Hamza 's report.
Hamza said that LA was the biggest city in the USA, but I'm sure that New York is bigger.
But even in this case using "is" would also be correct.