ISLAMABAD (AFP) - Around 25,000 supporters of Pakistani politician Imran Khan gathered in Islamabad late on Thursday, enthusiastically waiting for the ex-cricketer to address them by video link from hospital.

The charismatic 60-year-old has been ordered by doctors to remain immobile after suffering fractured vertebrae and a broken rib on Tuesday after falling from a stage at a rally in Lahore ahead of Saturday's elections.

The injuries prevent him from attending in person the final rally for his Pakistan Tehreek-e-Insaf (PTI) party, which is looking to make a breakthrough for the first time at the polls, before campaigning ends at midnight.

But Mr Khan's absence did nothing to dampen the festive spirits of the crowd, estimated by one police and a city official at between 25,000-30,000, who poured into the street outside parliament.

Songs blared out from a large public address system in front of a sea of the red-and-green PTI flags being waved by young men and women.

"I miss Imran Khan and wish he could be at this wonderful rally. I don't think his absence will dampen, but rather boost our morale," said 21-year-old student Hassan Ali.

But despite his electrifying campaign, a question mark hangs over how well Mr Khan will do, considering he won only one seat in 2002.