LAHORE, Pakistan, March 12 (Xinhua) -- Four back-to-back blasts occurred on Friday evening in eastern Pakistan's Lahore, injuring four people, police sources said.

The first blast occurred in the backyard of a police station near Moon Market area, Iqbal Town, injuring four people. Heavy smoke can be seen blowing from the scene.

Eyewitnesses told media said that the explosives were dug in the ground and blown up in evening. The blast shattered the windowpanes of nearby buildings and shops.

Pakistani investigators inspect a car damaged by an explosion in the residential area of Lahore, Pakistan on Friday, March 12, 2010

After a while, three more blasts occurred in succession in different places of the same area.

The second one took place in a car which was destroyed completely. No casualties have been reported.