Crowds of protesters are gathering in Belgrade for a massive rally in the Serbian capital seen as a culmination of months-long protests against populist President Aleksandar Vucic.

Hundreds of thousands of people descended on Serbia's capital on Saturday to protest over the deaths of 15 people in a railway station collapse. While the government put attendance at 107,000 across Belgrade, an independent monitor said 325,000 - if not more - had gathered, making it Serbia's largest protest ever.

The rally on Saturday in the capital, Belgrade, came as protests have spread to towns around the country and have drawn increasingly insistent calls that President Aleksandar Vucic step aside.