Two suicide bombers blew themselves up at a police checkpoint at the entrance to Pakistan's city of Lahore late Monday, wounding seven people, a senior police official said.
The bombers struck after dark in a congested area near bus terminals on a link road to Pakistan's intercity motorway.
"A car was stopped at the checkpost and the two suicide bombers in the car exploded themselves. We have found legs and a head," city police chief Pervez Rathor told reporters at the scene.
"One warden and two constables were critically wounded and four civilians are also injured."
Rathor said the car was packed with a huge quantity of explosives and "could have caused a catastrophe" had it entered the city.
"Bomb disposal staff are defusing remaining explosives in the car. Thank God no one died," he added.
Private Geo television showed security officers inspecting a small mangled car in front of a truck and a few other vehicles on a wide road where low concrete blast barriers were visible in front of the damaged car.
There were small pieces of debris scattered across the road.
Mohammad Akram, a police driver who witnessed the bombing, said the car did not stop at the first barrier and, when it approached another, policemen in front of it raised their guns.
"When policemen took the occupants of the car on at gunpoint, one of them came out of the car and blew himself up as the other man was still sitting in the car," Akram said.
The incident happened on a link road to the motorway that dissects the country from the northwestern city of Peshawar to the capital Islamabad and east to Lahore.
Pakistan has been on full security alert for weeks, following a surge in bloodshed blamed on Taliban and Al-Qaeda-linked militants.
A suicide bomber killed 35 people outside a bank and hotel complex near Pakistan's army headquarters in the garrison city of Rawalpindi earlier on Monday.