Pakistani soldiers on patrol in Karachi
Pakistan: Karachi terror attack kills dozens after gunmen open fireAthar Hussain/Reuters file photo

At least 47 people have been killed and several injured after gunmen sprayed bullets on a bus in Pakistan's biggest city Karachi.

Several women are thought to be among the dead. Local reports suggest at least eight men entered the passenger bus and opened fire before fleeing the scene on motorbikes.

Most of the victims are believed to be from the Ismaili Shiite community, which has come under several attacks in the past.

Ghulam Haider Jamali, inspector general of Sindh province, was cited by Pakistani daily Dawn as saying that six gunmen entered the bus and executed 43 passengers. Most victims are believed to have been shot in the head.

"The bus had a capacity of 52 passengers but it was overloaded and dozens of people were boarding it. Most of them were from the Ismaili community," a police officer, who was at the scene, told Pakistani daily Tribune.

About 60 people were on the bus when the attack took place. Some of the injured are in a critical condition. Leaflets containing militant content have been found at the attack site.

Preliminary reports suggest the assailants used 9mm pistols, and empty Kalashnikov shells were also found strewn around the site.

Prime Minister Nawaz Sharif condemned the attack as authorities continue to probe.

According to reports, panic has gripped large parts of the city.

Though no group has formally claimed responsibility for the present attack, the Pakistani Taliban, locally called Tehreek-e-Taliban, is known to have targeted religious minority groups.