document: Dr Imran Farooq, a leader of Karachi's influential MQM party, was stabbed to death near his home in Edgware, north London in September 2010.
  Khalid Shamim and Mohsin Ali were detained near the Pakistan-Afghanistan border in Chaman, Balochistan province.
  They are to be handed to Pakistan's Federal Investigation Agency.
  The BBC's Shahzeb Jillani in Pakistan says the murder was widely seen as a politically-motivated killing because Dr Farooq was reportedly planning to break away from the MQM leadership in London and start a new party.
  The arrested suspects and a third man named Mohammed Kashif Khan Kamran worked for the MQM party, officials said.
  In a statement, the MQM party denied any association with the suspects or involvement in the murder of Dr Farooq and accused the Pakistani government of political victimisation.
  Dr Farooq was parliamentary leader in the Pakistani National Assembly when he went into hiding during a military operation against the MQM (Muttahida Quami Movement party) in 1992.
summary: Pakistan authorities have detained two men suspected of being involved in the killing of an exiled politician in London five years ago, officials say.