| Pakistani security officials collect evidence from the scene of a blast in Lahore. |
Security officials had cordoned off the area on Bedian Road in the bustling capital of Punjab province after the blast, which rescuers said occurred just before 08:00am local time.
"It appears to have been an act of terrorism," Punjab provincial law minister Rana Sanaullah said in televised comments, adding that two soldiers and two civilians had been killed.
Rescue officials and police confirmed the toll, with a police official telling AFP the census team had been the target of the attack.
Teams of enumerators backed by the military and security forces are carrying out Pakistan's first census in almost two decades, an enormous and highly charged task that could redraw the country's political map one year before national parliamentary elections.
"Four people are dead so far and at least 18 injured, who were shifted to hospital," said rescue spokeswoman Deeba Shahnaz. The police official said at least 10 people had been wounded.