A bomb explosion wounded seven paramilitary ranger officials in Karachi on Thursday, officials said.

The incident took place in the city's eastern neighbourhood of Landhi, close to Gulshan-e-Buner area, which is said to be hiding militants.

"A roadside remote controlled bomb planted on a motorbike went off near a vehicle carrying 10 ranger officials, wounding seven of them," senior local police official Faisal Noor told AFP.

He said condition of two injured officials was critical.

A local intelligence official also confirmed the incident.

Rangers are currently taking part in a joint operation with police in Karachi aimed at cleansing the city of terrorists and other hardcore criminals including hired killers, gun runners and drug peddlers.

Karachi, a city of 18 million people which contributes 42 percent of Pakistan's GDP, has been plagued by sectarian, ethnic and political violence for years.