Media playback is unsupported on your device Media caption The BBC's Aleem Maqbool said thousands had turned up for the rally

Tens of thousands of people have turned out at a rally in the southern Pakistani city of Karachi for former cricketer turned politician Imran Khan.

Mr Khan, who has been an established politician for many years but has struggled to win votes, has seen his support increase recently.

Correspondents say he has been riding a wave of disillusionment, particularly among the urban middle class.

The next national elections are scheduled for 2013.

'Potent power'

The BBC's Aleem Maqbool, at the rally, says there were posters, banners and T-shirts espousing hope - clearly reminiscent of the sentiment that carried President Barack Obama to office in the US.

One supporter there told the BBC: "I'm highly optimistic that Imran Khan has the potent power to bring in change which we highly need because our country can't survive without a fair and just leadership.

Image copyright AFP Image caption The turnout in Karachi was large, given Mr Khan's traditional support base is in Punjab province

"It doesn't matter that he's a cricketer or something else. Whatever he is, he is not a diplomat, he is not a liar."

But our correspondent says that despite winning support from many disillusioned Pakistanis, Mr Khan still has a lot of work to do to clarify exactly what he stands for and whether he really does have the ability to lead the country out of its troubles.

The two main parties - the PPP and the PML-N - are still strongly entrenched and Mr Khan has yet to spell out the specific policies of his Pakistan Tehreek-e-Insaf (Movement for Justice) party.

One policy Mr Khan has won support for his opposition to US drone strikes on militants inside Pakistani territory.

He also argues that foreign aid is fuelling corruption and should be stopped.

Mr Khan has won over key defectors such as the PPP's Shah Mahmood Qureshi and Javed Hashmi of the PML-N.

The turnout in Karachi was large, given Mr Khan's traditional support base is in Punjab province.