An explosive device went off inside a truck on Monday night in Lahore, the capital of Pakistan's Punjab province, injuring at least 22 people, police said.

The blast happened at Bund road area, which is part of the route former prime minister Nawaz Sharif had finalised for his return to Lahore from Islamabad on Wednesday.

An official of the ruling Pakistan Muslim League-Nawaz (PML-N) said Sharif's route in the city would be revised now.

Police and rescue officials have cordoned off the area. A rescue official told PTI that an explosive device hidden inside the truck went off at around 9 pm local time.

The kind of device and the explosives used were not yet known.

"At least 22 people have been injured and shifted to hospitals. A minor girl is stated to be critical," he said.

DIG Haider Ashraf confirmed that it was a bomb blast.

"The device was planted in the fruit truck," he said, adding a huge crater has developed at the site of the blast.

"We have launched investigation on all aspects," he said.

Azim Hanif, an eyewitness, said he was going to the parking stand in the area when a powerful blast took place.

"Due the impact of the blast, I fell on the ground. After a couple of minutes when I gained my senses, I saw some people injured," Hanif said.

The explosion shattered the windows of nearby buildings. A number of bikes and cars were damaged due to its intensity.

Lahore, the cultural capital of Pakistan, has witnessed several terror attacks in recent months.  -- PTI

Representative image.