"A suicide bomber today blew himself up near the police lines at Qila Gujjar Singh. Six persons have been killed and eight wounded," Lahore police chief Amin Wains told reporters.
"The suicide bomber wanted to enter the police headquarters but failing to do so he blew himself up near it," Wains said.
The bomber could not enter the police headquarters due to elaborate security arrangements, he said.
Jamat-ul-Ahrar, a splinter group of the Tehreek-e-Taliban Pakistan (TTP), claimed responsibility for the attack.
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"We want to make it clear to the rulers that we will take revenge for the blood of innocent Muslims -- our operations will continue till Islamic system is imposed," Jamat-ul-Ahrar Spokesman Ehsanullah Ehsan said.
The bombing is dedicated to all the "martyrs who were dragged out of prison and killed or hanged," he said.
The rescuers and other civic agencies shifted the injured to Mayo and Sir Ganga Ram hospitals. Among the injured are two young police women and a 10-year-old boy.
The police headquarters houses over 5,000 police officers.
"I was taking tea on a roadside restaurant when I fell on ground with the impact of deafening sound. Although I did not fall unconscious but for a few moments my vision got blurred," Faisal Ali, who works at a private airline office, said.
"I rushed back to my office where I saw broken windowpanes and the furniture damaged. Everyone in the office were thanking God for being safe," he said.