Pakistan is set to start the second phase of a controversial plan to send undocumented Afghan refugees back to their country.

Beginning Sunday, authorities are likely to expel more than 800,000 Afghans from the country, after about 541,000 were forced to leave in the first phase in November last year.

If they do not leave voluntarily, the refugees face arrest and deportation.

Before the first phase of repatriation, the Pakistani government claimed there were nearly 4.4 million Afghan refugees, out of which an estimated 1.73 million were undocumented.

The government has defended the crackdown, citing security concerns and a struggling economy.

The deportation order came amid a dramatic increase in armed attacks across Pakistan, with the government attributing the attacks to groups and nationals based in Afghanistan, an allegation the Taliban government in Afghanistan rejected.

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