The nature of the blast was not immediately clear.
Rescue 1122 teams shifted the injured policemen and civilians to nearby hospitals, where an emergency has been imposed. Police said they are investigating.
Washington on Thursday offered a $5 million bounty for the Pakistani Taliban militant leader, Mulllah Fazlullah, a day after a suspected USA drone strike on a training camp in a remote part of Afghanistan killed his son and more than 20 other militants preparing to launch suicide attacks in Pakistan.
At least one person was killed and 20 others injured including several policemen on Wednesday evening in a blast in Pakistan's eastern city of Lahore, local media and police said.
According to rescue officials, a caller who informed them about the incident said it was a cylinder blast.
The main country's Taliban group Tehrik-e-Taliban Pakistan claimed responsibility for the bombing, saying it was a suicide attack.
In a tweet, Punjab province's government "strongly condemned" the attack. Khan has asked the CCPO Lahore and all RPOs and DPOs to strengthen security in their respective regions and districts. Around 25 people were also injured in the attack. He directed that all measures be taken to ensure safety of the life and property of the masses.
At least 45 people were injured in an explosion in a fruit truck stationed in a parking lot on Band Road in August previous year.
"A suicide bomber riding a motorcycle attacked the police", Ashraf said.
A suicide attack near a software technology park in Lahore killed 26 people and wounded over 50 in July a year ago.
In February previous year, 18 people were killed, including several police officials, and more than 80 wounded in a suicide attack during a protest on a busy intersection of Lahore.