The two Christians were accused of blasphemy, he said, adding they and family members had fled their homes.
Blasphemy is punishable by death in Pakistan and though no one has ever been executed for it, numerous accused people have been lynched by outraged crowds.
A Christian leader, Akmal Bhatti, said the crowd had "torched" at least five churches and looted valuables from houses that had been abandoned by their owners.
Several social media posts showed some churches, houses and belongings on fire as police stood by.
The mob was made up of thousands of people led by local clerics, mainly from an Islamist political party called Tehreek-e-Labaik Pakistan (TLP), a government source said.
Persons:
Naveed Ahmad, Shakil Masih, Usman Anwar, Anwar ul Haq Kakar, Akmal Bhatti, Asif Shahzad, Angus MacSwan, Nick Macfie
Organizations:
Reuters, REUTERS, REUTERS Acquire, Caretaker, Thomson
Locations:
LAHORE, Pakistan, Jaranwala, Faisalabad, Islamabad