The blast, one day after the beginning of the holy month of Ramadan, took place close to the Data Darbar, one of the largest shrines in South Asia.
“It was an attack on police that left several dead and dozens of policemen and civilians injured. The target was police,” said Syed Mubashir Hussain, a spokesman for the Lahore police.
The attack follows a period of relative calm in the city, where attacks were at one time common.
No casualty details were immediately available but the Dawn newspaper reported that at least three people had been killed.
“A rescue operation is under way and we have shifted 15 people to hospital,” said Muhammad Farooq, a spokesman for the city’s rescue services, Reuters reported.
There was no immediate claim of responsibility.