Security forces in Pakistan have fired live rounds in the air and used tear gas to try to control anti-government protests.Television pictures also showed demonstrators throwing stones at a rally in Islamabad organised by the Sufi cleric Tahirul Qadri.His supporters said the crowds prevented the cleric from being arrested by government forces.Mr Qadri claimed the size of the crowd gathered on the main avenue leading to the government quarters was four million, but that figure is hugely exaggerated.City officials have put the number of protesters at roughly 30,000, which is in line with pictures streaming on Pakistani news networks.Mr Qadri is a new - and possibly powerful player - in the opaque world of Pakistani politics.He has just arrived in the country after spending many years in Canada and has set himself up as a champion of the people, pushing an anti-corruption agenda.His call for widespread reforms has presented the ruling Pakistan People's Party with a massive headache.It is blamed across the country for being corrupt, failing to deal with a growing Taliban insurgency, huge power shortages and an economy in freefall.But many Pakistanis are sceptical about Mr Qadri's motives.It is widely rumoured that he has the backing of the country's powerful military and is being used as a pawn in the run-up to the country's elections - which are expected to be held in May.Mr Qadri is calling for the poll to be suspended indefinitely until Pakistan's endemic corruption is cleared up - something that would play into the army's hands as it could assume the role then of a caretaker government indefinitely.Some analysts suggest this has the all the hallmarks of a soft coup in the making.The military denies backing him, and it is far from clear where his campaign's finances come from.