Watch: Bulldozers tear down Afghans' houses in Pakistan
Pakistan has given 1.7 million undocumented foreigners, most of them Afghans, until 1 November to leave or face deportation.
Over 20,000 people rushed to cross the border the day before the deadline.
Ahead of the deadline, structures described by officials as illegal houses of Afghans were torn down in the suburbs of Islamabad and elsewhere.
Ahmen Jan, who has been living in Karachi for 30 years, said his family had to leave all its belongings behind.
Many face uncertain futures back in Afghanistan, where the Taliban government imposes a strict interpretation of Islamic law.
