At least 15 people were killed and 16 others injured on Saturday in an explosion in Pakistan's Karachi, local police said.

Police spokesperson Sohail Jokhio said that the explosion was likely caused by accumulated gas in the sewer system beneath a bank building.

"So far 15 people have died & 16 were brought injured. 8 of the injured have been discharged after treatment while the remaining 8 are still being treated. 2 of the injured are in critical condition," Karachi's administrator Murtaza Wahab wrote in a tweet.

"Investigation is going on to ascertain the cause of the blast & necessary treatment is being provided to the injured," he tweeted earlier.