According to the police, the improvised explosive device (IED) was planted in a flower pot at a roadside at Boat Basin in the up market Clifton area of the city.
"The target was apparently a vehicle carrying some foreigners which was escorted by rangers and passed through," one officer said on condition of anonymity.
"The miscreants set off the device but it didn't go off as planned and instead its ball bearings and other particles spread all over the road," he said.
Geo News reported that the van apparently was carrying 11 foreigners when the IED was set off.
Police also discovered some 11 homemade bombs in a shop which was damaged in Landhi after one of the IEDs went off accidentally in the afternoon.
"It was a kabari shop and after the minor explosion took place it was partially damaged. More search yielded 11 more home made bombs from the shop whose owner is under investigation now," the official said.