Deputy Inspector General of police Haider Ashraf said the bomb exploded when the police were changing guards at the checkpoint just outside an annual religious congregation in the suburb of Raiwind on Wednesday.
"I can at the moment say that police was the target," Ashraf said.
Jam Sajjad, a spokesman for emergency services, said a motorcycle was used in the explosion.
Shahid Waheed, a senior government official in Lahore, confirmed that "more than 20 people have been wounded and taken to hospitals,"
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