A video emerges purported to show vote rigging at a polling station during Pakistan's general elections.
A woman is seen stuffing stacks of papers into a ballot box in Karachi.
Different mobile phone footage was shown to journalists by independent candidate, Munsif Ali Khan.
In an undisclosed tribal area, ballot papers are seen scattered on the ground and gunfire is heard in the background.
Reuters cannot verify the authenticity of any of these videos.
Hundreds demonstrated against the alleged vote rigging.
"We protest" they chanted in Islamabad.
(SOUNDBITE) (Urdu) SAIMA OMAR, SECRETARY-GENERAL OF WOMEN'S WING OF IMRAN KHAN'S PAKISTAN TEHREEK-E-INSAF (PTI) PARTY, SAYING:
"In the Punjab, especially in Lahore, and in Sindh in Karachi, rigging went on openly and votes were changed. First they created a delay and then they carried out wrong counting."
In Karachi over five hundred supporters for candidate Imran Khan staged a sit-in.
